DEPARTMENT OF EMBRYOLOGY. 115 



cells; G. W. Corner has studied the development and finer histology 

 of the corpus luteum. 



The study of mitochondria has been the object of considerable atten- 

 tion in the department during the year. E. V. Cowdry has continued 

 his researches on the mitochondria of the spinal ganglion cells. He 

 finds them throughout the whole series of vertebrates and states that 

 they are characterized by the constancy of their morphology, distri- 

 bution, amount, and micro-chemical properties. There is a reciprocal 

 relation between the amount of mitochondria and lipoid granules in the 

 spinal ganglion cells. Dr. Cowdry believes that they are connected 

 with the metabolic acti\'ity of the nerve-cells. Observations on the 

 Nissl bodies show that these bodies are not visible in the unstained 

 cells. In the fixed or stained cells they appear either as definite bodies 

 or, especially in small cells, as a diffuse amorphous deposit. Cowdry 

 records some observations which apparently support the idea that the 

 Nissl bodies are not preformed in the living cell, but result from the 

 coagulation of this amorphous substance. 



The same author has turned his attention to the vital staining of 

 mitochondria with janus green and diethyl safranin in human blood- 

 cells. Mitochondria can be demonstrated by these vital stains in the 

 lymphocytes, large lymphocytes, finely granular leucocytes, and occa- 

 sionally in the coarsely granular leucocytes and platelets of normal 

 adult human blood. They are totally absent in the non-nucleated red 

 blood-cells of the adult. These two observations are in accord with the 

 current conceptions of the physiological significance of mitochondria 

 and show that mitochondria are to some exent indicators of cellular 

 activity, for they are present in the active stages of cytomorphosis 

 (lymphocytes, large lymphocytes, and finely granular leucocytes), and 

 absent in the terminal or later stages (non-nucleated red blood-cells). 

 Cowdry further points out that the term ''non-granular leucocyte" 

 is in reality a misnomer, for the so-called non-granular leucocytes all 

 contain mitochondria. 



Cowdry's conclusion regarding the absence of mitochondria in the 

 red blood-cell of the normal adult is confirmed by the researches of 

 P. G. Shipley; but Shipley shows further that the young non-nucleated 

 erythrocytes contain mitochondria. The presence of mitochondria is 

 a character of the youth of these cells, and this character may be useful 

 in chnical researches in diseases which increase the activity of the 

 hematopoietic organs. 



M. R. and W. H. Lewis have found the tissue cultures of chicken 

 embryos an excellent material for the study of the mitochondi'ia in the 

 living cell. They find that the mitochondria are almost never at rest, 

 but are continually changing their position and also their shape. The 

 changes in shape are truly remarkable, not only in the great variety of 

 forms, but also in the rapidity with which the change is made from one 



