MITOCHONDRIA VARIATIONS IN NERVE CELLS 331 



MATERIAL AND ME FHODS 



White mice of known age were used. Care was taken that they 

 were in good condition. They were killed with chloroform, thus 

 reducing the possible factor of fright to a minimum. They were 

 then fixed by injection through the blood vessels of a mixture 

 of formalin and bichromate so as to guard against the production 

 of mechanical injury on removal of the brain as well as to insure 

 a good penetration of the fixative. Sections were stained ac- 

 cording to the method recommended by Cowdry ('16 b, p. 30), 

 the essentials of which follow: (1) a fixation by injection, through 

 the blood vessels, of a mixture of neutral formalin and potas- 

 sium bichromate; (2) a mordanting in bichromate, followed by 

 dehydration and imbedding in the usual manner; and (3) a 

 staining of the sections, cut 4 microns in thickness, with fuchsin 

 and methyl green. The fuchsin stains the mitochondria a 

 bright crimson color and the methyl green colors the Nissl 

 substance in the same cell green, thus giving a good color con- 

 trast between the two. Specimens were also stained with iron 

 hematoxylin and by the Benda method, for control. They 

 gave results confirmatory in every way. 



The observations are based upon actual measurements of mito- 

 chondria which were made by using one of the new Spencer wheel 

 ocular micrometers. Each measurement was made five times 

 and the average taken so as to reduce the experimental error as 

 far as possible. 



OBSERVATIONS 



Morphological variations. A general survey of the central 

 nervous sj'-stem was made and it became at once evident that 

 the mitochondria did present considerable variation in form in 

 different types of nerve cells. Nerve cells of the same kind, m 

 the same nuclei, generally contained the same form of mito- 

 chondria. Somewhat more individual variation appeared in 

 cells of the spinal cord, spinal ganghon and Gasserian ganglion, 

 due perhaps to mechanical injury on removal. Mechanical 

 manipulation and faulty technique will bring about great varia- 



