362 GENERAL PROPERTIES OF MUSCLE AT REST. 



would be if the extension were in direct proportion to the 

 weight, but will be a curve, sinking very rapidly at first, but 

 afterwards more and more slowly, and so continually tending 

 to run parallel to the abscissa line ; in fact, it will be an hyper- 

 bola. 



Obs. III. Neither of the above set of observations is quite 

 correct : to eliminate the effects of exhaustion, the observations 

 should be repeated on the muscle within the body (see Chap. 

 XIX., sec. XI.), and time allowed between each observation 

 for the muscle completely to recover itself. 



Obs. IV. Kill the muscle (either the same or a fresh one) by 

 immersing it in water at 40 C. for five minutes. 



Repeat Obs. I. and II. on the muscle so-killed. It will be 

 found that there is far less extension of the muscle, which, after 

 the load has been removed, does not return to its original 

 length. 



The dead muscle, as compared with the living one, is more 

 elastic, i. e., is less extensible ; but its elasticity is very imper- 

 fect, i. e., the original length is not regained. 



II. Reaction. Obs. V. Having pithed a frog, place a ca- 

 nula in the aorta, slit open the right auricle, and drive all the 

 blood out by injecting the normal saline solution, which should 

 be perfectly neutral. Dissect out the gastrocnemius of one 

 side with clean instruments, and with a very clean knife cut it 

 across through the middle of its belty. Take two slips of lit- 

 mus paper, one faintly red, the other faintly blue ; press the 

 cut end of one-half of the muscle on one piece, and the other on 

 the other. On the red litmus paper will be left a distinct blue 

 mark where the muscle was pressed ; on the blue litmus paper 

 there will be no mark at all, or, if any, a change in the direc- 

 tion of red, which is distinctly less red than the blue mark on 

 the red litmus is blue. 



The reaction of living muscle, freed as much as possible from 

 blood, is faintly alkaline. 



Obs. VI. Kill the corresponding muscle in the other leg by 

 immersion in water at 40 C. Test as in Obs. V. The blue 

 litmus paper will be marked most distinctly red ; the red not 

 altered. For this a much stronger blue paper may be used. 

 The reaction is permanent, and therefore is not due to carbonic 

 acid. 



Muscle, in dying, on entering into RIGOR MORTIS, becomes dis- 

 tinHly acid. 



Obs. VII. Keep any of the above rigid muscles covered in a 

 damp warm place. Test the reaction from time to time. The 

 acid reaction gives way to an alkaline one. which increases 

 rapidly in intensity, and soon far exceeds the natural alkaline 

 reaction. This secondary alkalinity arises from decomposi- 

 tion. 



