78 PHYSIOLOGY (.)! Mrsri.Ks AND NERVES, 



the greatest amount of waiinth during tetanus, during 

 which no nj.jK'n nl labour i~ accomplished. The whole 

 intern;,! w..il< !' the miivle is in \}\\> case transformed 

 into warmth, thus rai>ing the t emperat are of the muscle- 

 substance ; and (lie amount of this warmth may, as we 

 liiive seen, be at least approximately measured and 

 calculated. 



3. One result of the chemical changes which occur 

 within the muscle during its activity, is naturally 

 tint part of the constituent matter of the muscle is 

 expended, other matter being dep,,>ited in its place. 

 As long as the muscle remains uninjured within the 

 body of the animal, part of the matter thus formed is 

 carried away, and fresh nutritive matter is brought to 

 replace the expended material. The products which 

 arise by decomposition during the activity of the 

 muscle may therefore be indicated in the blood of the 

 animal, and from the blood they are removed from out 

 of the body by special excretory organs. Accordingly 

 we find that the amount of carbonic acid excreted is 

 considerably increased by muscular labour, and that 

 the other products of muscular decomposition, such as 

 creatiu and the urea arising from the latter, lactic acid, 

 \e., reappear in the urine. The more abundant Iv 

 the blood-current flows through the mu-cles. the more 

 quickly are the products of decomposition removed 

 from the muscle. This is of course possible onlv in a 

 very inferior degree when the mii>cle has been cut out 

 from the body. Tlii-i-the rea>oii \\liy ;m extracted 

 muscle retains its power of activity I'm- but a very short 

 time. If, for instance, such a muscle is eont inuoiisl v 

 tetanised, it will be found that the contraction, though 

 it is at first very considerable, \ery soon decreases and 



