MACERATION PROCEDURES 9 



ganisation. For example, addition of salts may vary the pro- 

 portion of albumin and globulin found on electrophoresis of 

 plasma. Somewhat similar effects are found on simply adding 

 water to plasma, and a not immoderate addition of water causes 

 precipitation of part of the globulin. It is difficult to see how 

 experiments on the isolation of granules and other small cell 

 organs can be taken at their face value unless it is rigorously 

 demonstrated that their composition is unchanged by the isola- 

 tion procedure. 



Often, if the composition of individual granules is identical or 

 closely similar to the granules in the living cells, there still re- 

 main many difficulties in interpretation of experiments on the 

 mass isolation of granules — mitochondria, nuclei, etc. The rea- 

 son for this is that it is practically impossible, except in a small 

 minority of tissues, to obtain a homogeneous concentration of 

 cells. In the first place, almost all tissues contain, in addition 

 to the typical cellular component, cells of the vascular system, 

 connective tissue cells, and white and red blood cells. More- 

 over, often the cells of the same type, e.g., hepatic cells, are 

 not of identical chemical composition in closely adjacent parts 

 of an organ. Consequently, it does not follow that a biochemi- 

 cal pattern observed in a particular group of granules is identi- 

 cal with, or even similar to, that of any individual cell type. 

 This can be very simply demonstrated in the case of hepatic 

 cells. Long-chain aldehyde (Feulgen's plasmal), ribonucleic 

 acid, and alkaline phosphatase will occur in the same granule 

 fraction obtained from liver. It would, therefore, be natural to 

 suppose that these three components are bound together in the 

 same granule and may even cooperate in carrying out certain 

 biochemical functions. When, however, the distribution of these 

 three components is studied in tissue sections, it is found that 

 each of them is present to a significant concentration only in 

 some of the hepatic cells. Some hepatic cells may be practically 

 free of any one of these components, some may contain one 

 component, some, two components, and some, three components 

 in significant quantities. If, therefore, all three substances 

 are present on a granule of the same size in the living cells, 

 then it appears that some of the granules contain none of the 

 substances, some, one of the substances, some, two, and some, 



