BY DR. MICHAEL FOSTER. 363 



At the same time the muscle will be found to have become 

 very extensible, with scarcely any elasticity. 



6bs. VIII. Divide a fresh muscle in two. Immerse for a 

 few minutes one half (A) in water at 40 C. ; the other (B) in 

 boiling water. Test the reaction of both. 



A will be acid, from development of rigor mortis. 



B will be alkaline. Before rigor mortis had time to set in, 

 the albumin of the muscle was coagulated. This coagulation 

 set free a quantity of alkali (see Chap. XXXY.) ; hence its re- 

 action. 



III. Transparency. 06s. IX. Take from a frog a portion 

 of any one of its thin flat muscles. The mylohyoid is the most 

 convenient, but the sartorius (fig. 278 s.), or any other thin 

 muscle, will do as well. The muscle must be perfectly fresh 

 and irritable, and care must be taken that at least the middle 

 portion of muscle is not in the least injured. Place the muscle 

 in normal saline solution, or serum, on the unheated " warm 

 stage," and examine with a quarter-inch object-glass. 



Focus down through the middle (least injured) portion of 

 the muscle, upon some object (bloodvessel, etc.) underneath 

 the fibres. The distinctness with which this object is seen will 

 be a measure of the transparency of the muscular tissue. 



Keeping the eye fixed upon the above-mentioned object, heat 

 the stage. It will be found that when the temperature of the 

 muscle has risen to 40 C. (or a little below), the object is no 

 longer so distinct as before, or has even become totally invisi- 

 ble. 



On entering into rigor mortis, the muscular fibre becomes 

 opaque. 



Living muscle is very_xtensU)l, with perfect elasticity, of 

 alkaline reaction, and considerable transparency. On enter- 

 ing into rigor mortis it loses its extensibility, its elasticity 

 becomes imperfect, its reaction acid, and its transparency 

 gives place to opacity. 



