516 OF RESPIRATION. 



(CHAP. xiv. Sect. 2), the motor powers of the Pneumogastric are chiefly due, 

 take their origin in the Medulla Oblongata itself. But we must not decide upon 

 the connection of a particular nerve with a particular segment of the Spinal 

 Cord, simply because it diverges from it at that point; and the analogy of the 

 Invertebrated classes favors the idea that a direct structural connection exists 

 between the ganglionic centre of the Respiratory movements, and the nerves 

 which transmit their influence to the muscles. Upon this point, however, it is 

 unsafe to speculate ; and we can only state it as a possibility, that some such 

 connection may be established in Vertebrated animals through the white columns 

 of the spinal cord. 



551. That the Respiratory movements, as ordinarily performed, are essen- 

 tially independent of the Will, appears not only from our own consciousness, 

 but also from cases of paralysis; in some of which, the power of the will over 

 the muscles has been lost, whilst the movements have been kept up by the reflex 

 action of the Medulla Oblongata or respiratory ganglion; whilst in others, some 

 of the respiratory muscles have been motionless during ordinary breathing, and 

 yet have remained under the power of the will. 1 That consciousness is not a 

 necessary link in the chain of causes which produce the respiratory movements, 

 we are enabled to judge from the phenomena presented by the human being in 

 sleep and . coma, by anencephalous foetuses, and by decapitated animals. This 

 conclusion is confirmed by a case recorded by Dr. H. Ley, 3 who had under his 

 care a patient in whom the pneumogastrics appeared to be diseased; the lungs 

 suffered in the usual way in consequence, and the patient had evidently labori- 

 ous breathing ; but he distinctly said that he felt no uneasiness in his chest. 

 The experience of every one informs him that the Respiratory movements are 

 partly under the control and direction of the will, though frequently unre- 

 strainable by it. In ordinary circumstances, when the blood is being perfectly 

 aerated, and there is a sufficient amount of arterial blood in the system to carry 

 on the functions of life for a short time, we can suspend the respiratory actions 

 during a few seconds without any inconvenience. If, however, we endeavor to 

 prolong the suspension, the stimulus conveyed by the excitor nerves to the Me- 

 dulla Oblongata becomes too strong, and we cannot avoid making inspiratory 

 efforts ; and if the suspension be still further prolonged, the whole body becomes 

 agitated by movements which are almost of a convulsive nature, and no effort 

 of the will can then prevent the ingress of air. 3 It is easy to understand why, 

 in the higher animals at least, and more especially in Man, the respiratory ac- 

 tions should be thus placed under the control of the will: since they are sub- 

 servient to the production of those sounds, by which individuals communicate 

 their feelings and desires to each other ; and which, when articulate, are capa- 

 ble of so completely expressing what is passing in the mind of the speaker. If 

 the respiratory muscles of Man were no more under his control than they ap- 

 pear to be in the Insect or Molluscous animal, he might be provided with the 

 most perfect apparatus of speech, and yet he would not be able to employ it to 

 any advantage. 



1 Such cases are mentioned by Sir C. Bell, in the Appendix to his work on the Nervous 

 System. 



2 "On Laryngismus Stridulus," p. 417. 



3 It is asserted by M. Bourdon (" Recherches sur le Mecanisme de la Respiration," p. 

 21), that no person ever committed suicide, though many have attempted to do so, by 

 simply holding the breath ; the control of the will over the respiratory muscles not being 

 sufliciently great, to antagonize the stimulus of the "besoin de respirer," when this has 

 become aggravated by the temporary cessation of the action. But such persons have suc- 

 ceeded better, by holding the face beneath the surface of water ; because here another set 

 of muscles is called into action, which are much more under the control of the will than 

 are those of respiration; and a strong volition applied to these can prevent all access of 

 air to the lungs, however violent may be the inspiratory efforts. 



