DEPARTMENT OF EMBRYOLOGY. 79 



year. This work was started in the University of Zurich, and. since his asso- 

 ciation with the Johns Hopkins Medical School, Dr. Huber has continued his 

 program of a broad comparative study of this nerve-muscle group and has 

 extended it to the negro. In cooperation with Dr. Walter Hughson, he has 

 been able to confirm his morphological observations on the innervation of the 

 facial musculature by experimental studies in the cat and dog. In narcotized 

 animals the facial musculature was laid bare and the nerve branches were 

 stimulated with a weak electric current and the respective contractions 

 recorded. In other animals the different branches of the facial nerve were 

 sectioned, after which the resultant paralysis was determined, and in these 

 animals the investigators were able to demonstrate resultant degeneration in 

 the facial-muscle groups belonging to the different branches. 



GENITO-URINARY ORGANS. 

 Development of Kidney in Chick Embryos. 



A striking example of the desirability of combining the study of living tissues 

 with that of fixed serial sections, where one is studying the development of an 

 organ, is afforded by the important results that were obtained in this way by 

 Dr. W. F. Rienhoff, in his work on the development of the metanephros in the 

 chick and which have made it possible for him to give a very complete account 

 of this morphogenetic process. He made spreads of living tissue taken at 

 different stages of development, and also transferred small pieces of the 

 kidney primordium to a culture medium, and, after incubating them for vary- 

 ing lengths of time, studied them both in the living state and after fixation 

 and staining. For certainty in orientation, these were then compared with 

 the same structure as seen in serial sections. In this way he was able to 

 demonstrate the high degree of specificity that exists in nephrogenic tissue. 

 The small transplanted particles tend to acquire their predestined form, 

 regardless of the foreign environment and the absence of pressure of surround- 

 ing structures; the collecting tubules grow in a straight line and the secreting 

 tubules always become convoluted. Dr. Rienhoff was able to observe every 

 step in the development of the glomerulus, which has heretofore been one 

 of the puzzles for the embryologist. Together with its capillaries and blood 

 elements, it differentiates in situ from the cellular mass that makes up the 

 distal end of the convoluted tubule. It is not invaginated like a cup, with an 

 ingrowth of capillaries, as has been generally supposed; the lumen forms 

 within the cell-mass by virtue of a rearrangement and separation of the cells, 

 which leaves a thin layer of epithelial cells (Bowman's capsule) on one side 

 and a mass of epithelial and endothelial cells on the other (glomerulus) . The 

 form of the convoluted tubule is the result of the differential growth of its 

 component cells, its various bends and curvatures not being simply accidental. 

 As the lumen forms, it is possible actually to observe the uniting of the con- 

 voluted and collecting tubules which occurs at a definite place. The blood 

 system surrounding the metanephric tubules is at first principally sinusoidal, 

 the circulation taking place by diffusion between the sinuses and peripheral 

 capillaries, as in the pronephros and mesonephros. From the first the 

 tubules are completely enveloped in an endothelial membrane. Later, the 

 sinusoidal system is almost entirely replaced by capillaries, and direct con- 

 tinuity is then established with the peripheral system. 



