BY DR. KLEIN. 67 



red color, the mucous membrane is pencilled away and the re- 

 mainder covered in glycerin. The mesentery of the newt, the 

 iris, or the muscular coat of the intestine of mammalia may 

 be prepared in the method already explained, and then treated 

 in every respect as just described. Chloride of palladium, 

 which has also been used for the coloring of muscular fibres, 

 has no advantage over the gold salt. In sections of unstriped 

 muscle, previously hardened in one-eighth to one-fourth per 

 cent, solution of chromic acid, and subsequently colored in pic- 

 ric acid, carmine, aniline, &c., the muscular bundles are dis- 

 tinctly seen, as well as their relations to each other, and to 

 the septa of connective tissue which surround and separate 

 them. 1 



In sections through the hardened intestine of the frog, rab- 

 bit, or rat, the muscular cells, where they are seen in longitu- 

 dinal section, appear to be separated from each other, not by 

 straight lines, but by marginal borders, which exhibit fine trans- 

 verse markings, referable to the existence of minute furrows, 

 which run in a direction vertical to the axis of the fibre. 



To isolate the individual muscle-cells for the study of their 

 form and nuclei, macerating liquids, by which the interstitial 

 substance is disintegrated, are employed. Small fragments are 

 introduced into a dark sherry-colored solution of bichromate 

 of potash, two or three per cent, acetic acid mixture, nitric 

 acid diluted with four times its volume of water, or thirty-five 

 per cent, potash solution. The arrangement of the nerves of 

 unstriped muscle will be described in a future chapter. 



SECTION II. STRIPED MUSCLE. 



The tissue of striped muscles consists of long cylinders (mus- 

 cular fibres) which are united by connective tissue into bundles 

 (fasciculi) of varying length. The following parts have to be 

 considered : The contents of substance of the individual fibre 

 with its muscle-corpuscles ; the sarcolemma ; and the junction 

 of muscle with tension. The mode of ending of the nerves in 

 muscle will be described in the next chapter. 



Proper Substance of Muscular Fibre. The leg of a 

 water-beetle (Hydrophilus) is torn out, and its horny covering 

 removed. A snip is then taken from the exposed muscular 

 mass, with the aid of curved scissors, or a fine scalpel, and at 

 once covered without addition. If the cover-glass is then 



1 Fine sections of structures containing numerous unstriped muscu- 

 lar fibres, which have been hardened in chromic acid, then placed for a 

 few days in diluted alcohol, and finally stained in a weak ammoniacal 

 solution of carmine, exhibit a striking contrast between the muscular 

 fibres and the connective tissue, the former being tinged yellow by the 

 chromic acid, the latter red by the carmine. 



