190 OF MUSCULAR MOTION. 



but in which I have never been able to detect genuine 

 irritability. 



Such are the lacteals, glands, gall-bladder, uterus, 

 the dartos, and the penis. (B) 



And others, with no less impropriety, bestow it upon 

 the iris, the external surface of the lungs, &c. in which 

 it no more exists than in the cellular membrane and 

 those parts which arc composed of it, the common 

 internments, membranes of the brain, pleura, perito- 

 nseum, periosteum, medullary membrane, tendons, 

 aponeuroses, &c. or in the proper parenchyma of the 

 viscera, (20) of the liver, spleen, kidneys, secundines, 

 the brain, and the rest of the nervous system, every 

 one of which parts is destitute alike of muscular fibre 

 and of what is peculiar to it, irritability. 



302. As we find muscular irritability sometimes con- 

 founded with the contractility of the mucous web ; so, 

 on the other hand, some eminent men, particularly in 

 modern times, have attributed it to the nervous energy * 



Now, although we cannot deny the influence of the 

 nerves upon the muscles, most strikingly shewn of 

 late (225) by the experiments of the celebrated Galvani 

 and others, and although no muscular fibril, however 

 minute, can be found absolutely destitute of nervous 

 pulp, we are not on this account to assert that irrita- 



* To this point chiefly relate the celebrated disputes respecting the influew. 

 of nerves upon the motion of the heart, and the modus operand! of opium upon 

 the heart and nerves. 



Consult, besides other authors already quoted, 



Rob. Whytt, Essay on the vital and other involuntary motions of animals.. 

 Edmb. )751. 8vo. ; and more at large in his Works, ib. 1768. 4to. 



J. Aug. Unzer, erste Griindc ciner Physiologic dtr eigentlti'hrn thierisirftc. 

 Natur thierifi-hcr Kiirpcr. Leipzig. 1771. 8vo. 



