XXVII. THE MEDICAL SCIENCES

Cytology.-Cowdry (Am.

ANATOMY

G. CARL HUBER

Jour. | NaHCO, and 0.25 grams of dextrose Anat., xix) considers the general added to 100 cc. of the sea-waterfunctional significance of mitochon- bouillon mixture, a favorable culture dria, which he defines as substances medium is obtained. Stockard (Am. occurring in the form of granules, Jour. Anat., xviii) reports on the derods and filaments in almost all liv- velopment and wandering of mesening cells, reacting positively to janus chymal cells in embryos of the teleost, green and resembling phospholipins Fundulus heteroclitus. The yolk sac and to a lesser extent albumins (see is clear and is covered by only a sinalso XXV, Zoology). Evidence is gle layer of ectoderm, enabling obserpresented showing that mitochondria vation at different stages of developplay an active role in cell activity, ment in living eggs. The wandering perhaps on the constructive side of cells begin migration from the edge metabolism. They play no clearly of the germ shield when the embryo demonstrable part in histogenesis and is about 40 hours old. At 60 hours there are at hand no conclusive obser- four distinct types of mesenchymal vations showing that they do or do not cells may be differentiated: black play a role in heredity. In the study chromatophores, which ultimately of pathologic conditions mitochondria form pigmented syncytia which surmay furnish an index of cytoplasmic round the vitelline vessels; brown activity. Scott (ibid., xx) reports on chromatophores, not so large, remain the behavior of the mitochondria in separate, are branched and also atthe pancreas cells in phosphorus poi- tached to vessel walls; elongated spinsoning, finding that they are the first dle-shaped cells, which at 48 hours constituents of the cytoplasm to show aggregate in definite groups, later arpathologic change. Shipley (Anat. range in linear cords and become tuRec., x) has shown by means of vital bular vessels; small globular cells, staining with janus green that cer- which develop into colored blood cells. tain granules of trypanosomes are mi- E. R. Clark (Anat. Rec., xi) presents tochondrial in nature; the kinetonu- the results of a study of the reactions cleus was found to stain like mito- of mesenchymal cells in the tadpole chondria. Rasmussen and Myers tail toward injected oil droplets, in(Jour. Comp. Neur., xxvi) have stud- jected to test the hypothesis that the ied the chromatolytic changes in the differentiation of blood and lymph encentral nervous system of the wood- dothelium may be stimulated by the chuck during hibernation, reporting mechanical pressure exerted on the that they could not detect any modi- mesenchymal cells by the accumulafication in the Nissl granules charac- tion of fluid. The behavior of inditeristic of hibernation, when com- vidual cells toward droplets of sterile pared with the non-hibernating state. paraffin oil was observed for days in Lewis (Anat. Rec., x) has investigat- the living tadpoles. No special reaced sea water as a medium for tissue tion was noted. W. G. Clark (ibid., culture. She finds that if the sea wa- x) has shown by experimental methter is made isotonic with the plasma ods that living connective tissue reof the form from which cultures are acts to the presence of a smooth nonto be made and ten parts of bouillon irritating foreign body in such a way made from the muscle of the form in that there results a distinct pavement question is added, with 0.02 grams of layer of flattened cells. These results

are said to argue against a specificity ovulation, fertilization

and early

of endothelium and mesothelium. cleavage stages bear the same time Shipley (ibid.) reports finding hæmo- relation to parturition in both suckglobin-bearing cells in tissue cultures ling and non-suckling mice. Imof the primitive area vasculosa, for plantation in the uterus in non-suckthe most part abnormal in form and ling mice takes place on the fifth day size (see also XXV, Zoology). The following parturition; in suckling observations show that the life of mice with three or more young, on cells in cultures is not merely a series the 14th day following parturition, of survival phenomena. Spaeth (Jour. the blastulas lying free in the lumen Exp. Zool., xx) presents morphologi- of the uterus from the sixth to the cal, embryological and physiological 14th day. Swift (Am. Jour. Anat., evidence that the melanophores of xviii) has considered the origin of fishes, amphibia and reptiles are func- the definitive sex cells in the chick tionally modified smooth-muscle cells, and their relation to the primordial and that the color changes in these germ cells and reports on observaforms are brought about by the physi- tions on the histogenesis of the goological response of special smooth- nads in the female chick. He finds muscle cells. Laurens (ibid.), in an that during the two days subsequent experimental study on the melano- to the development of the germinal phores of Amblystoma larvae, finds epithelium (about 321⁄2 days) the mathat they are adaptive in that they jority of the germ cells are found in respond either to relative intensity this tissue. During the sixth and of light or to the color and intensity seventh day of development the gerof the background. The eyes possess minal epithelium by proliferation an important control over the melano- forms medullary cords, including a phores, the epiphysis not. Allen few primordial sex cells. In the male (Anat. Rec., x) presents results of an these cords form the seminiferous extended series of experiments on tubules and contain the majority of methods of fixation, dehydration and the primordial sex cells. In the feembedding. A modified Bouin's male, beginning with the eighth day fluid to which urea is added is rec- and extending to the 11th day, active ommended for fixation and an ap- proliferation of the primordial sex paratus for gradual alcohol concen- cells of the germinal epithelium octration during dehydration is sug- curs, giving rise to lobulations which gested. Cell mitoses in brain and appear on the under surface of the testis tissue were specially investi- germinal epithelium, forming cortical gated. (See also XXV, Zoology.) cords which contain the oögonia Development and Growth.-Hart- which develop into the definitive ova. man (Jour. Morph., xxvii) has contributed an excellent account of the cleavage and early blastocyst stages of the opossum; the blastocyst is complete with about the 40-cell stage (see also XXV, Zoölogy). Spurgeon and Brooke (Anat. Rec., x) report on implantation and early segmentation stages of the opossum (see also XXV, Zoology). The first cleavage plane is meridional, resulting in two equal blastomeres. The second cleavage is in the equatorial plane resulting in smaller cells at the animal pole. Kirkham (ibid.) has endeavored to ascertain the cause of the prolongation of the gestation period in suckling mice. From a study of a long series of embryonic stages obtained from both suckling and nonsuckling mice, it was found that

E. L. Clark (ibid.) reports on a study of the lymph flow in the early superficial lymphatics in living chick embryos varying in age from 51⁄2 days to nine days. In the primitive superficial plexus as found in the fifth day there is no lymphatic circulation, the lymphatics containing blood cells, the pressure in the veins with which the lymphatics of certain regions are connected, being higher than in the lymphatics. As the pressure in the lymphatics is established a feeble lymph flow is observed. The formation of definite lymph channels is due to lymph flow and mechanical factors. Squier (Anat. Rec., x) finds that the pulmonary blood circuit is established in the 72-hour chick, though not necessarily in its definite form. Definite conclusions as to the

ultimate origin of the pulmonary | for denying their distinctive branchveins were not reached. Watt (Car- iomeric organ character. This is negie Inst., Wash., Contrib. to Em- especially emphasized with reference bryol., Pub. No. 222) presents a very to the thymus, the development of careful description of twin human which is regarded as a reaction deembryos with 17 to 19 paired somites. generation, presenting a typical epiThe detailed account is based on to- thelial growth with altered relation tal and partial reconstruction of one to the mesenchyme. Locy and Larof these embryos, with a study of sell (ibid., xix and xx) present an the serial sections of both of them. excellent account of the development The external form of the embryos and of the avian lung, tracing the formathe state of development of the noto- tion of the bronchi, air sacs and rechord and somites, of the alimentary, current bronchi from anlage to the vascular, urogenital and nervous sys- adult stage. The development of the tems are in turn considered. Pro- recurrent bronchi and of the air sacs nephric tubules with Wolffian duct and the establishment of intercomare present in the ninth to tenth munications between all parts of the segments. No mesonephric tubules bronchial passages give the bird's are as yet developed. The two em- lung a unique structure differing bryos are almost exact duplicates from that of other vertebrates. although they are not identical or Kernan (Jour. Morph., xxvii) gives real twins. Bremer (Am. Jour. a detailed description of the chonAnat., xix) in an investigation of the interrelation of the mesonephros, kidney and the placenta in different classes of mammalian embryos notes that mammalian embryos may be divided in two classes: those which retain a functional mesonephros until the kidney is capable of excretion, and those in which the mesonephros degenerates before the kidney is capable of excretion. In animals with early degeneration of the mesonephros the placenta is provided with an apparatus similar to the glomeruli of the mesonephros, appearing in the placenta at about the time when the mesonephros degenerates. In the placenta of mammals with a continuous embryonic urinary secretion no such placental structure differentiates (see also XXV, Zoology). Bremer (Anat. Rec., x) describes mesonephric tubules in the anterior region of the mesonephros of ruminants which present fused corpuscles and no glomeruli but with capillaries in relation with all sides of the glomerular cavity; these differ from the usually observed mesonephric corpuscles. Kingsbury (Amer. Jour. Anat., xviii) presents observations on the development of the human pharynx, based on wax reconstructions of the pharyngeal region of human embryos of varying ages. The branchial pouch derivatives are serially considered as to their morphogenesis and arguments presented

drocranium of a 22-mm. human embryo reproduced at a magnification of 75 diameters by means of the Born wax-plate method, comparing his findings with observations of Van Noorden, Jacobi, Levi and Macklin, who have studied and modeled the chondrocrania of younger and older human embryos. Shipley and Macklin (Anat. Rec., x) report that regions of new bone formation, before the deposition of lime salts is evident, can be vitally stained by the introduction into the peritoneal cavity of a sterile one per cent. solution of trypan blue. Preparations may be fixed in neutral formalin and cleared or decalcified and studied in sections. Donaldson (The Rat, Mem. No. 6, Wistar Inst.) gives a comprehensive review of the literature dealing with the structure and physiology of the albino and Norway rat. summary of the excellent observations on growth phenomena of the albino rat conducted by Donaldson and his coworkers is presented with numerous growth curves and tables. King (Anat. Rec., x) has studied growth of body and of the nervous system in albino rats undersized at birth. It was found that undersized individuals are not necessarily runts, but may attain normal adult size. All of the rats are not born with equal capacity for growth even under most favorable conditions. Body weight at birth indicates the prob

A

frontalis or the anterior ethmoidal | comparable to the basophilic mesamecells. The naso-frontal duct and boid cells of the embryonic circulathe ethmoidal infundibulum are in tion. They are derived from endothe majority of cases discontinuous thelium, become detached and contribchannels, but may be in direct con- ute to the cellular elements of the tinuation. Kush and Boas (Anat. circulation. They are found to be Rec., x) have investigated the carry-intimately associated with developing angle in the forearm, finding that mental processes involving atrophy in the female it is about three degrees of certain aortic branches and in pig smaller than in the male and that the embryos are present in embryos havright carrying angle is about three de- ing a length from five to 15 mm. regrees smaller than the left. In left- spectively. This observer (ibid., xx) handed individuals the right and left has also investigated certain cellular carrying angle is about equal. Jordan elements found in the celomic cavity (ibid.) reports on a study of the myo- and mesenchyme of mammalian emfibrils in the leg muscle of the sea bryos. In pig embryos, five to 12 mm., spider. The banding in uncontracted a basophilic macrophage type is myofibrils is described and figured. found. The macrophages present Contraction appears to be due to a structural variations correlated with shortening and thickening of the myo- functional activity. The evidence fibrils with streaming of the stainable seems clear that these cells are desubstance from the M to the Z mem-rived from the celomic mesothelium. branes. (See also XXV, Zoology.) The eosinophilic nonphagocytic cells Blood and Lymph-Vascular Sys- of the celomic cavity very probably tems.-Danchakoff (Anat. Rec., x) represent degenerating erythrocytes. presents an investigation on the wan- Jordan (Am. Jour. Anat., xix) has dering cells in the loose connective investigated the microscopic structure tissue in birds, considering their his- of the yolk sac of pig embryos with togenesis. In the connective tissue special reference to the origin of the of birds a certain number of wander- erythrocytes, finding pig embryos of ing cells are normally found. These 10 mm. the most suitable, for in this are developed from mesenchymal stage the yolk sac attains its highest cells by withdrawal of processes, the degree of differentiation (see also cell becoming mobile. Environmental XXV, Zoology). The entoderm cells conditions determine further develop- are thought to contain presecretion ment. The mesenchyme is polyvalent filaments. The mesenchyme of the in its potencies of development. The yolk sac was found to differentiate experimental results in tissue graft- directly into endothelium or into ing give strong support to the mono- hematoblasts. Hematoblasts were phyletic view of the origin of the dif- also found to differentiate from the ferent blood cells. This observer endothelium. This author (Anat. (ibid.) has further presented a sum- Rec., x) presents evidence to show mary of observations on the origin of that the yolk sac of pig embryos is red blood cells from the viewpoint of an active source of hematoblast origin the monophyletic school. It is the from the endothelium, since transicontention that in early embryonic tion stages from primitive endothestages there is present a common lium to erythrocytes are observed in mother cell, of mesenchymal origin, for suitable stages. Reagan and Thoringthe several types of blood cells. This ton (ibid.) have studied the vascumother cell is present in the adult larization of the embryonic body of organism and becomes a source of dif- hybrid teleosts without circulation. ferentiation and regeneration of blood The observations give evidence of a cells, and probably also of their path- local origin of endothelium from the ological proliferation. Emmel (Am. mesenchyme, also that vessels or vesJour. Anat., xix) contributes a study sel anlagen are hemophoric, blood of certain cell clusters found in the cells having been found in vessel anventral part of the dorsal aorta of lagen disconnected from the circulamammalian embryos (see also XXV, tion and blood islands. Reagan Zoology). The cells of these clusters (ibid.) has also studied the vascular present cytological characteristics tissue in chemically treated fish em