The relations di' iiiitixlioinlii:! ;iih1 ntln r cyf o|ilrisiiiic fonstitiieiits <-tr. 4^7 



Moreover, in llic cusc oT otlnT li\;iti\r>. tlic (■>■]]> ncaici' tin- centre 

 of tlio block iiHcii incseiit ;i >liriiiikcii m- \ ;iciinl;iiei| ciiiiditiiiii t'ai- 

 iVdlll IKillllill. 'I'lie cllief eNceplidli^ In this 'jelieia li/at ioli ncciir ill tllH 

 inetallic iiiiprciinatinn^ nt CoIlìì and <';ij;il. in wliich ihe (iiitvjdf cdls niv. 

 tV(M|ii('iitly destroycd. ("aie must llieiclnie lie taken in tin- inteijifetat imi 

 of ai>pe;iiiiiices in the cytoplasm of cells lyiiiii' deeply in a mass of 

 tissue, i)articularly wlion that tissue lias been lixed in a lluid tin-; 

 constituents of wliich vaiy widely in peiietfatini:- iiowef. because we 

 tlieu Imve to deal with tlie ivsult of the successive or accumulative 

 actiou oi tliese ingredients. 



Given a good fixation, the stains and conibimiîions of stains whicli 

 may be employed successfully for mitocliondiia are Icuion. In oider 

 to obtain and keep permanently pre|)aiations. the balsam emjiloyed 

 should be as nearly neutral as possible, no iicat should be used t(j 

 accelerate its hardening, and the specimens should imt be exposed 

 for any considerable time to bright light. 



4. The relation of the neurosomes of Held to inilochoiidria. 



It has already been shown that Held described two types of 

 granules under the single heading of neurosomes. 



The first type consists of the erytlirosin-stained neurosomes. and 

 the question arises as to whetluM- they are artefacts due to the meth- 

 ods of fixation employed. The fact that they are seen after a o-j-eat 

 variety of fixations, namely: neutral fornmlin. formalin-Zenker. strong 

 Flemming, trichlorlactic acid, chi'ome-sublimate. etc.. is against this 

 view. 



Mitochondria are the only kiunvn structures in the nerve cell 

 with which they may be confused. After (dironie-sublimate fixation 

 both they and the mitochondria may be stained by tlie'i- respective 

 methods. Neutral safranin gives preparations (fig. 11) in which both 

 these granules are stained in the same cell and may be distinguished 

 from oneanother, though with difficulty, since the gi-anules of type 

 I are 1. of irregular size and shape. 2. stain Avith variable intensity, 

 always however less brilliautlv than the niitochondria. and 3. because 



