148 THE MITOCHONDRIAL CONSTITUENTS OF PROTOPLASM. 



in wliich they are embedded— some variation in fluidity, refractive index, or elec- 

 trical state, for instance. And conversely, the absence of any noticeable reaction 

 on the part of the mitochondria does not exclude the possibiUty of their participa- 

 tion. Interpretation is extraordinarily difficult. The methods of tissue culture, 

 if rigidly controlled, may prove of service. 



The most pressing need, however, is for further knowledge of the chemistry 

 of mitochondria, for, when chemical facts come in at one door, superstition inva- 

 riably vanishes at the other. Here also the difficulties seem almost insurmount- 

 able, because we have had to rely upon indirect and roundabout methods. If it 

 were possible to make a direct chemical analysis of mitochondria it would place 

 the whole work, once and for all, upon a secure foundation, but doing this involves 

 very special training and it is hard to see the way. It might be possible, as I have 

 already suggested, to partly separate out mitochondria by means of the centrifuge 

 and then collect them for analyses by some of the recently devised methods of 

 cell dissection. It would seem that some such procedure might be of use in the 

 analysis of many other cytoplasmic constituents. Should it prove feasible it would 

 have a most illuminating effect upon the whole question of the constitution of 

 protoplasm. 



EXPLANATION OF FIGURES OF PLATE. 



Figures 1, 3, 5, 6, 10, and 13 have been drawn from preparations fixed in Regaud's formalin and bichromate 

 mixture and stained with fuchsin and methyl green. Figure 7 was drawn from material fixed in the same way 

 but stained with iron hematoxylin. In making the drawings Zeiss apochromatic objective 1.5 mm., compensating 

 ocular 6, and camera lucida were used giving a magnification of l,.50O diameters. 



Fia. 1. Kidney-cells of white mouse. ,.,,.., ui i ii •. u j • ■ *i, • u i 



Fia. 2. Cells of trapezoid nucleus of white mouse, remarkable for the large block-hke mitochondria in the peripheral 

 cytoplasm (after Nicholson, 1916). , ■ , , 



Fig 3. Vesicula seminalis of white mouse. Note the absence of blebs on the mitochondrial filaments and the 

 stages in the production of the secretion. 



Fig. 4. Large anterior horn nerve-cell of white mouse (after Nicholson, 1916). 



Fia. 5. Prostate of white mouse containing very minute mitochondria. 



Fig. 6. Ovarian egg of white mouse containing for the most part granular mitochondria. 



Fig! 7. Serous celk of parotid of mouse with very fine rod-Uke mitochondria. 



Fig. 8. Thyroid vesicle (after Bensley, 1916). . , , . , ^, 



Fig 9. Pancreas (after Scott, 1916), with typical bleb-like swellings on the mitochondrial filaments. 



Fig lo! Inte.stinal epithelium of white mouse with bipolar arrangement of mitochondria. 



Fig u! I..arge cell of mesencephahc nucleus of the fifth nerve with small cell of locus coeruleus adjacent (after Nichol- 

 son, 1916). Note the difference in the mitochondria. 



Fig. 12. Large pyramidal cell of hippocampus (after Nicholson, 1916). 



Fig. 13. Thvnius of white mouse, showing large mitochondria in the small round cells, tiny mitochondria in the 

 epithelial cells, and an apparent absence of mitochondria in the mast cell. 



