6 E. V. COWDRY 



cells. In the former he observed them in the fonn of granules, 

 and, in the latter, as granules and very tiny rods. This differ- 

 entiation apparently (p. 620) applies to the large and small 

 cells of the spinal ganglion as well as to those found in other 

 parts of the brain. There can be no question that the bodies 

 which he described as mitochondria are mitochondria. 



Rana 



Altmann ('90) also observed and figured (plate 11, fig. 2) 

 structures in the spinal ganglion cells of the frog which may be 

 identified with mitochondria for reasons similar to those already 

 given in detail in the case of the cat. 



Duesberg ('12, p. 809) made some observations on plastosomes 

 (mitochondria) in the ganglion cells of tadpoles, but is unwilling 

 to arrive at any conclusion regarding them. 



Petromyzon marinus Lin. and Ammocoetes hranchialis Block 



Mawas ('10, p. 126) investigated the structure of the spinal 

 ganglion cells of these two forms by the Regaud method. His 

 description apparently applied to the former. He found that 

 in the adult the nerve cells may be divided into two groups, the 

 large ones and the small ones. In the small cells he found gran- 

 ules and filaments, distributed throughout the cytoplasm, elec- 

 tively stained in black with the hematoxylin. The larger cells 

 differ in that the cytoplasm is less intensely stained and that 

 there are present in addition a number of vesicles which are 

 considerably larger than the granules and filaments. These 

 vesicles seem to be more numerous in the region of the nucleus 

 but they extend into the dendritic processes as well. Where 

 they are absent the granules and filaments take their place. 

 He concluded that the granules and filaments of the small cells 

 are mitochondria and that the vesicles are allied to them. 



It is doubtful whether the descriptions of Furst ('02), Motta- 

 Coco and Lombardo ('03) and Motta-Coco ('04) relate to 

 mitochondria. 



