CELL -ORGANS 



^IiTOCHONDRiA are minute intra-cellular structures having 

 certain distinctive characters, viz. : — 



They are of low refractive index, and give a characteristic reac- 

 tion with the dyestuff termed Janus Green, even in a solution as 

 dilute as 1 in 500,000. Further, they are composed as a substance 

 that is very soluble in alcohol, acetic acid, and many other fixa- 

 tives. 



As their name implies, they are often of thread-like appearance, 

 but other shapes are well recognised, although no animal has 

 mitochondria of a form peculiar to itself. It is, however, very 

 striking that similarity of function seems to be associated with 

 similarity in the shape of the mitochondria. There is no very 

 obvious orderly arrangement of these structures in most cells, 

 although in the kidney they are collected in the basal parts of the 

 cells, i.e., next to the blood vessels. Indeed in all other glands 

 which always secrete in the same direction, the mitochondria are 

 arranged at the end of the cell furthest from the glandular lumen. 

 In the intestine the conditions are peculiar because mitochondria 

 are piled up at both ends of the cells, presumably as an indication 

 of the dual function of secretion and absorption. 



In 1898 Golgi described certain cytoplasmic components in 

 nerve cells. These structures, now usually known as the Golgi 

 apparatus, present a peculiar contorted or basket-like arrange- 

 ment. At about the same time as Golgi's publication, Holmgren 

 had discovered and described certain clear canals in animal 

 cytoplasm. These, in form, arrangement and position, so much 

 resembled the Golgi apparatus, that the two structures were often 

 regarded as being one ; a view no longer held. 



The Golgi apparatus is an area of cytoplasm, often of reticular 

 form, and of variable size, sometimes being as large as a nucleus. 

 The material of which the structure is composed is in part soluble in 



3 1—2 



