6 



DIGESTION. 



dominal muscles forcibly press the stomach 

 against the diaphragm, so as to assist the anti- 

 peristaltic motion of that viscus. Magendie 

 made experiments to show that unless the dia- 

 phragm or abdominal muscles acted on the 

 stomach, no vomiting could take place. He 

 went too far, however, when he attributed the 

 entire result to them. Substituting a pig's 

 bladder for the stomach, he injected tartar 

 emetic into the veins, and vomiting followed. 

 But he forgot that pressure might readily 

 empty a dead bladder and have little effect on 

 a living stomach. And that such is the case 

 we may be certain, else every cough would 

 evacuate the stomach. 



Lastly, the diaphragm acts the part of a sep- 

 tum or mediastinum to separate the two great 

 cavities between which it is placed. When 

 this septum is wanting, the abdominal viscera 

 get into the thorax, and in such cases the lungs 

 are constantly found in a rudimentary state : 

 their further evolution being impeded by the 

 pressure exerted on them by the intruding 

 viscera.* 



It has been stated that the oesophageal open- 

 ing may be closed by those fibres of the crura 

 which curve round it. The other openings, as 

 the aortic, and that for the ascending cava, can- 

 not be diminished by the efforts of the muscle. 

 This is plain from the tendinous margins which 

 they present, and the manner in which the mus- 

 cular fibres are attached to their borders. 



We have not mentioned some of the uses 

 which the ancients ascribed to the diaphragm 

 as, that it is the seat of the passions,f that it 

 prevented noxious vapours from rising into the 

 thorax, that it fanned the hypochondria, and so 

 forth. These are too fanciful to demand serious 

 notice. 



Malformations and diseases. The dia- 

 phragm may be absent in whole or in part by 

 congenital malformation. In the very young 

 foetus the thorax and abdomen form one cavity, 

 as in birds, reptiles, and fishes; and the deve- 

 lopment of the diaphragm, as of most other 

 organs, is by a process of growth from the cir- 

 cumference to the centre. If, therefore, an 

 arrest of formation occur at a very early period 

 of fetal existence, the muscle may be entirely 

 wanting; if at a later period, some deficiency 

 will be found at or near the centre. An exam- 

 ple of the total absence of the diaphragm was 

 dissected by Diemorbroeck. The subject lived 

 to the age of seven years without suffering any 

 inconvenience except a frequent cough.J Con- 

 genital deficiencies near its jniddle are not very 

 rare. They are observed oftener towards the 

 left than the right side, and are always accom- 

 panied with a protrusion of the abdominal 

 viscera into the thorax, not vice versa. The 

 development of the thoracic viscera is impeded 

 by this intrusion, and they remain more or less 



* Andral's Pathological Anatomy, tr. by Town- 

 send and West, vol. i. 



t The word phrenic, used with reference to the 

 diaphragm, as phrenic nerve, phrenic centre, &c. 

 has its origin in this opinion, ty>Evej, a <f>p>iv, mens, 



tanquam mentis sedes. 



\ Diet, dcs Sciences Med. art. Diaphragme. 



rudimentary. It sometimes happens that the 

 natural openings of the diaphragm are too 

 large, and then protrusions or herniae are apt to 

 occur by the sides of the tubes which they 

 were intended alone to transmit. 



Openings frequently occur in consequence 

 of disease or violence. Ulcers often make a 

 perforation, and it is common enough to see an 

 abscess of the liver make its way into the lung 

 through the diaphragm. The writer lately saw 

 an abscess, which formed in the gastrosplenic 

 omentum, take the same course. Wounds often 

 penetrate the diaphragm, and it is remarkable 

 that however small they may be, a ventral 

 phrenic hernia is sure to follow. 



The diaphragm has been suddenly ruptured 

 during violent muscular efforts, vomiting, falls, 

 &c. and instant death has usually followed. 

 Various examples of such ruptures are recorded 

 in the Dictionnaire des Sciences Med. art. 

 Diaphragme. The countenance in all such 

 cases assumes the peculiar expression or grin 

 called risus Sardonicus. 



The diaphragm is subject to attacks of in- 

 flammation, which, in almost every case, is 

 communicated to it by the adhering pleura or 

 peritoneum. It is indeed usually confined to 

 one or other of these serous membranes, chiefly 

 the pleura, and does not affect the muscular 

 fibre. It is, notwithstanding, termed diaphrag- 

 mitls. Hippocrates called it phrenitis, and 

 Boerhaave changed the name to paraphrenitis, 

 to distinguish it from a well-known cerebral 

 affection. 



Gangrene, collections of pus, tumours, &c. are 

 occasionally met with, and are of very difficult 

 diagnosis. 



Cartilaginous and osseous deposits have been 

 found on both sides of the diaphragm in the 

 subserous cellular tissue. 



The diaphragm is often considerably dis- 

 placed upwards or downwards. In ascites, 

 and in consequence of diseases of the liver and 

 of abdominal tumours, it may be pushed up to 

 the second rib on one side ; in thoracic affec- 

 tions again it has been so pushed down as to 

 become convex, in part of its extent, towards 

 the abdomen. Senac mentions a case of great 

 enlargement of the heart which caused the cen- 

 tral tendon to be buried in the abdomen, it 

 being formed into a kind of pouch.* Dr. W. 

 Stokes found the left ala convex towards the 

 abdomen in emphysema of the lungs,f and it 

 is known to yield extensively to the pressure of 

 fluid in cases of empyema, more especially if 

 the pleura covering it has been much engaged, 

 as the same accurate observer has noticed and 

 explained. 



For BIBLIOGRAPHY see that of Anatomy (INTRO- 

 DUCTION). 



(Charles Benson.) 



DIGESTION. (Yr. digestion; Germ. Ver- 

 dauung ; Ital. digestione.) This term is em- 

 ployed in Physiology to designate that func- 

 tion by which alimentary matter is received 



* Acad. des Sciences, Mem. 1729. 



t Dublin Med. Journal, vol. ix. p. 37. 



