38 THE STHLCTIKE OF CHKO.MOI'IJILE CELLS OF THE NEH\OUS SYSTE.^^ 



They are i)resent in the granule-cells of the cerebellum, as is also evident from the 

 earlier work of Altmann (1890, plate xiii. figure 1) and Xageotte (1909, p. 826), and 

 in the granule-cells of the olfactory bulb of mice and rats, which are well known to 

 be devoid of Xissl substance. IVIoreover, in certain cell-groups, under normal con- 

 ditions, there is often a variation in the mitochondria, as between different cells, 

 without any corresjxniding change in the Xissl substance. Mitochondria occur 

 abundantly throughout the length of the axone, where no Xissl substance has ever 

 been seen. They also occur in certain dendritic processes which do not contain any 

 Xissl substance. Evidence of this sort may be multiplied. 



Just how the mitochondria are concerned with the activity of the nervous 

 system is unknown. I have presented evidence elsewhere (1914, p. 18) that they 

 l)lay a part in the basic processes of metabolism which are comn^on to all cells, but 

 this is unfortunately a very broad statement and we naturally desire to learn some- 

 thing rather more specific about them. Coghill's (1915, p. 350) behef that the 

 mitochondria are concerned in the constructive (analx)lic) side of metabolism is of 

 interest in this connection, i)articularly since it falls so well in line with the well- 

 known " eclectosome " theory of Regaud (1911, p. 699), which, in turn, is an exten- 

 sion of the "side chain" theory of Ehrlich. M. R. and W. H. Lewis (1915, p. 393) 

 make the interesting suggestion that the mitochondria take jiart in cellular respira- 

 tion, which is also a fundamental i)roce.ss common to all cells. 



We may confidently exjiect that this new avenue of approach to the study of 

 the activity of the nervous system will yield results of importance, not onlj' because 

 our histological methods of technique are now sufficiently accurate to permit of the 

 actual enumeration of the mitochondria, a thing which can not be accomplished 

 in the case of the Xissl substance, but also because W'aldemar and Mathikle Koch 

 (1913, p. 427) have recently succeeded in devising chemical methods for the quali- 

 tative and (luantitative estimation of substances, very closely related, perhaps 

 identical with mitochondria, in the nervous system. These substances are phos- 

 pholijMns. Iloppe f^eyler long ago jwinted out that lecithin (a t>-i)ical phospholipin) 

 and cholesterol are to be foimd almost everywhere that life phenomena e.xist. In 

 fact, a great wave of revived interest is manifested in recent chemical and patho- 

 logical literature in these complex compounds of fatty acid, phosphorus, and nitro- 

 gen. Mathews (1915, p. 88) very aptly remarks that the phospholipins are the 

 most important substances in living matt(>r: 



"For they are fouiul in all cell.s, and it i.s uiKloubtedly their function to produce, with chole.sterol, 

 the peculiar semifluid, seiuisolid state of protoplasm. The latter holds much water in it, but it does not 

 dissolve. Indeed it may Ix' said that the phospholipins with cholesterol make the essential sub- 

 stratum of living matter. This physical substratum of phospholipin differs in different cells and 

 probably in the same type of cell in different animals, but everywhere, from the lowest plants to the 

 highly diflferentiatcd brain cells of mammals and of man himself, it possesses certain fundamental 

 chemical and physical properties. In all cases the phospholiiiin substratum is soluble in .-dcohol 

 containing some water," etc. 



In view of these considerations it is interesting to inquire whether the distribu- 

 tion of mitochondria in cells corresponds with that of the phospholipins. It is cer- 

 tainly true that mitochondria are more widelv distributed than anv other kind 



