IO2 NORMAL HISTOLOGY. 



Muscular Fibres Hardened with Osmic Acid. The 

 above-described finer structural details of the muscle 

 fibres are much more evident when they are in a state of 

 extension than when contracted. We may render this 

 condition permanent for study, by the following method : 

 the skin is quickly removed from the leg of a freshly-killed 

 animal (rabbit or dog), and one of the large muscles of 

 the thigh is forcibly extended with the fingers ; the canula 

 of a hypodermic syringe is then thrust into the muscle, 

 and an interstitial injection is made of a mixture of equal 

 parts of one-per-cent. solution of osmic acid and strong 

 alcohol. This fluid, in three or four minutes, fixes the 

 fibres in the extended condition. A small bit of tKat por- 

 tion which has become brown is now snipped off and 

 carefully teased and mounted in a mixture of equal parts 

 of glycerin and water. In such a preparation some of the 

 fibres frequently escape extension, in which case, the 

 marked difference may be observed between the extended 

 and non-extended condition of the fibres. 



Sections of Hardened Muscle. The details of the struc- 

 ture of muscular fibres, as well as their grouping and 

 relation to the connective tissue, may be well studied in 

 sections from hardened muscle. For this purpose the 

 tongue of some animal such as the dog is well suited, 

 since here we have short muscular fibres running in vari- 

 ous directions and attached to tendons, and we see in a 

 single transverse section of the organ, at once, longitudi- 

 nal, and transverse sections of the fibres. The tongue of 

 a dog is hardened in Mliller's fluid, and transverse sec- 

 tions through the anterior half of the organ are stained 

 double and mounted in glycerin. 



