8 CYTOLOGICAL TECHNIQUE 



Archoplasma was coined later to indicate the distinction between 

 ttiis material and the rest of the protoplasm.*^ It seems probable 

 that the archoplasm of blastomeres corresponds to the idiozome 

 of spermatogonia and other cells, though this has been 

 denied. ■^^ 



Sinuous rods or threads are seen in all parts of the cytoplasm ; 

 they are particularly abundant in the neighbourhood of the 

 idiozome, but they are never seen within the latter. These are the 

 thread-granules or mitochondria.^^ They often appear as granules 

 in fixed preparations, and not rarely as rows of granules; but 

 in life they are nearly always somewhat lengthened and usually 

 rod-shaped or filamentous. The diameter of all the mitochondria 

 in any one cell is commonly about the same, but the length varies 

 considerably: it is quite usual for the length and breadth to be 

 roughly proportional to those of a cigarette. The surface of 

 mitochondria is everywhere smooth, the ends rounded. Mito- 

 chondria very seldom branch. It is often said that they have a 

 capacity for independent movement, but it seems more likely that 

 motion is sometimes imparted to them by the ground cytoplasm. 

 We do not ordinarily see any objects in a cell that could be stages 

 in their growth from small rudiments, and there is strong reason 

 to believe that they usually multiply by transverse division. 



A quarter of a century ago much was known about the 

 arrangement of mitochondria in different kinds of cells, but very 

 little about their significance for vital processes. The discovery 

 that they could be separated in bulk by differential centrifuging of 

 mashed tissue^ ^ made it possible to subject them to detailed 

 chemical and enzymological analysis, and today we probably 

 know more about their mode of action than about that of any 

 other part of the cell, the chromosomes not excepted. We find 

 in them the enzymes concerned with the degradation of pyruvic 

 acid to carbon dioxide and water: that is to say, with the parts 

 of the respiratory process known as the tricarboxylic acid cycle 

 and the cytochrome system. It remains to relate their function to 

 the complex internal structure revealed by the electron-micro- 

 scope. 



Small lipid globules (lipochondria) are distributed in the 



