DEPARTMENT OF EMBRYOLOGY. 105 



These granules exhibit no definite behavior and disappear during 

 speriniogenesis. 



Dr. Paul G. Shipley describes in Trypanasoma lewisii granules 

 scattered through the cytoplasm which are more numerous at the 

 anterior end of the organism and show a marked tendency to clump 

 together at one or both ends of the nucleus. These granules are 

 stained in vivo with Janus-green, are dissolved by acetic acid, and in 

 permanent preparations (fixed and stained by the methods of Benda, 

 Bensley, Meves, and Altmann) give characteristic mitochondrial stain- 

 ing reactions. It is therefore highly probable that these granules are 

 mitochondria. Dr. Shipley found, furthennore, that the reactions of 

 the kineto-nucleus towards mitochondrial stains, both in fixed and in 

 vitally stained preparations, are very similar to those of the mito- 

 chondria, their behavior being analogous to that of the centrioles in 

 other cells. 



In the pancreas of the toad Mr. J. Albert Key has tried to elucidate 

 the relations of mitochondria to zymogen-granules, which some authors 

 believe to be very close. He injected the animals with pancreatic 

 secretion or pilocarpin and fixed the pancreas at various periods after 

 injection. He found on the filaments the spindle-like swellings that 

 have been interpreted as the first appearance of zymogen granules. 

 These swellings, however, do not stain with neutral gentian, neutral 

 safranin, or neutral red, nor are they fixed satisfactorily in Zenker 

 fonnahn material. On combining Bensley's neutral-gentian and 

 acid-fuchsin methods, which differentiates mitochondria from zymogen 

 granules, Key was unable to detect any difference between the swellings 

 and the rest of the filaments. He states further that there is an absence 

 of reciprocal changes in the number of mitochondria with variations 

 in the content of zymogen granules found by others in other material ; 

 and he is led to believe that the zjanogen granules are not formed 

 directly from the mitochondria. 



The purpose of the investigation conducted by Miss Madge DeG. 

 Thurlow was to determine whether the number of mitochondria could 

 be used as a basis for classifying nerve-cells into motor and sensory 

 groups. Although her results were negative, the investigation leads to 

 the interesting conclusion regarding the proportional number of mito- 

 chondria in cells belonging to the different nuclei of origin of the 

 cranial nerves in the white mouse, the number of mitochondria present 

 in each cell being determined by careful countings and measurements. 

 The cells of the mesenphalic nucleus of the fifth, the cochlear and 

 vestibular nuclei of the eighth, the nuclei of the sixth and seventh 

 nerves, seem to represent extremes in the number of mitochondria. 

 The largest number was found in the cells of the mesencephahc nucleus 

 of the fifth, the smallest in the cells of the nucleus of the seventh. 

 Large numbers of mitochondria were found also in the cells of the 



