their nerves exclusively from the great sympathetics, are obedient to the 

 will, and receive from the brain the principle of motion, the former, from 

 the branches which the sacral nerves send to the hypogastric plexuses : 

 the diaphragm, from the nerves which it receives from the fifth and sixth 

 cervical pairs. 



The great sympathetic nerves supply the diaphragm, the rectum, and 

 bladder, only with nerves of sensation. This provision was a very ne- 

 cessary one, for, if, as is the case with the heart, and the intestines, these 

 parts had received their nerves of motion from the great sympathetics, 

 their action would have been independent of the will, as is the case with 

 all the parts which these nerves supply with motion. The bladder and 

 rectum, placed at the extremities of the digestive apparatus, and destin- 

 ed to serve as reservoirs to the excrementitious residue of our solid and 

 liquid aliments, would have been constantly evacuating their contents, as 

 fast as the substances which are destined to be retained within them for 

 some time, reached their cavity. 



On the other hand, if the diaphragm had received its nerves of motion 

 from the great sympathetics, respiration would have ceased to be a vo- 

 luntary function, of which we might at pleasure accelerate, slacken, or 

 even completely suspend the action. To prove that the act of respira- 

 tion is under the controul of the will, we may have recourse to analogy, 

 and adduce the instance of reptiles, as lizards, frogs, serpents, salaman- 

 ders, and toads, which are cold-blooded animals, and in which this func- 

 tion is manifestly voluntary. We may further mention those slaves, who, 

 we are told by Galen, put themselves to death, when summoned before 

 their executioners or judges. According to thtet physiologist, and others, 

 they choked themselves by swallowing their tongue. But it is sufficient 

 to know how the muscles that bind down the tongue are situated, and the 

 degree of motion which they allow, to see how little ground there is for 

 that opinion. The action of the brain would, in that case, have been no 

 lotiger necessary to the maintenance of life ; in an animal without a brain, 

 respiration would have continued, and the circulation would not have 

 been interrupted. The death of that viscus would not have been attend- 

 ed with the sudden death of all the rest. 



The nerves which arise from the spinal marrow, and which give to the 

 diaphragm the power of contraction, a power which that muscle loses 

 suddenly, if these nerves be tied, appear to me the chief links which 

 unite the internal assimilating or nutritive functions, to those which 

 keep up the relation of the animal with external objects. Without this 

 bond of union, the series of vital phenomena would have been less close, 

 and their dependence less necessary. Had it not been for the necessity 

 that the diaphragm should receive from the brain, by means of the phre- 

 nic nerves, the principle which determines its contractions, acephalous 

 animals, which are born without that organ, might continue to live as 

 they did before birth, when the organs of nutritive life received blood, 

 which had undergone, in the lungs of the mother, the changes necessary 

 to life. But where the bond which united them to the mother is destroy- 

 ed, obliged themselves to produce in their fluids, the necessary changes, 

 by the inhalation of the vivifying principle contained in the atmosphere, 

 they no longer can obey that necessity; the organs of respiration are de- 

 ficient in the principle which should excite them. 



