442 E. V. COWDRY 



SUMMARY 



One is assailed with the feehng that we know very Httle about 

 mitochondria. This it would be foolish to deny. Therein lies 

 their charm. One also has the uncomfortable impression that 

 it is easy to prove that mitochondria can do anything by search- 

 ing the literature diligently for the required statements and 

 ignoring the rest. A great deal of work will have to be gone 

 over, confirmed and corrected. Certain it is, however, that we 

 can at least define them in microchemical terms as well as in a 

 morphological way. As far as breadth of distribution goes 

 they yield place to no other type of cell granulation. They 

 are as characteristic of the cytoplasm as chromatin is of the 

 nucleus. We know, further, that they are delicate indicators 

 of cell activity and we suspect many things. 



This line of study is to be considered as a revival of interest 

 in protoplasm. It may well be asked why we have not heard 

 of mitochondria long ere this? The reason is not far to seek. 

 It is the direct outcome of the tendency to neglect the cytoplasm 

 and to concentrate attention upon the nucleus on account of 

 the interest which seems to center in the nucleus from the stand- 

 point of heredity. The aim in making up fixatives was to show 

 nuclear detail. For this purpose mixtures containing either 

 alcohol, chloroform or acetic acid were employed because of 

 their rapid penetration. Now these substances destroy mito- 

 chondria. So that the more attention was focussed on the 

 nucleus the less chance there was for the observation of mito- 

 chondria. A vicious cycle was maintained. Happily a reaction 

 is now taking place, an equihbrium is being produced. 



This line of study has also developed parallel with the recent 

 tendency among physiological chemists and pathologists to 

 become interested in the phospholipins, which are complex 

 compounds of fatty acid, phosphorus and nitrogen and among 

 which we are inclined to group the mitochondria. Whereas, 

 formerly, their whole attention was devoted to the study of 

 proteins and was dominated by the tremendous impetus of 

 Emil Fischer's woi-k on protein synthesis, based as it was u}:)on 



