285 



tice of physic, has devoted to the consideration of this kind of affection. 

 It will be readily understood, that their occasional causes, the varieties 

 of which determine their different-kinds, exist in the heart or great blood-, 

 vessels, or act on the epigastric centre, and affect the brain only in a se- 

 condary manner. Thus, the kinds of syncope occasioned by aneurismal 

 dilatations of the hear* and great vessels, by polypous concretions formed 

 in these passages, by ossification of their parietes or of their valves, evi- 

 dently depend on the extreme debility, or on the entire cessation of the 

 action of the heart and arteries. Their parietes, ossified, dilated, ad- 

 hering to the neighbouring parts, or compressed by any fluid whatever, 

 no longer act on the blood with sufficient force, or else this fluid is in- 

 terrupted in its progress by some obstacle within its canal, as a polypous 

 concretion, an ossified and immoveable valve. Cullen, very justly, termed 

 these, idopathic or cardiac syncopes. 



To the above may be added plethoric syncope, depending on a con- 

 gestion of blood in the cavities of the heart: the contractions of this or- 

 gan become more frequent, it struggles to part with this excess of blood, 

 which is injurious to the performance of its functions: but to this un- 

 usual excitement, by which the contractility of its fibres is exhausted, 

 there succeeds a kind of paralysis necessarily accompanied by syncope. 



One may, likewise, include the fainting attending copious blood-let- 

 ting ; the rapid detraction of a certain quantity of the vivifying principle, 

 deprives the heart of the stimulus necessary to keep up its action. The 

 same effect is produced by drawing off the water contained in the abdo- 

 men, in ascites: a considerable number of vessels ceae to be compressed; 

 the blood, which they before refused to transmit, is sent to them in pro- 

 fusion; the quantity sent to the brain by the heart is lessened, in the same 

 proportion, and becomes insufficient for its excitement. Among the syn- 

 copes, called idiophatic, one may enumerate those occurring in the last 

 stage of the scurvy, the principal character of which is, an excessive de- 

 bility of the muscles employed in the vital functions, and in voluntary 

 motion; lastly, we may add asphyxia from strangulation, from drowning, 

 and from the gases unfit for respiration ; affections in which the blood 

 being deprived of the principle which enables it to determine the con- 

 tractions of the heart, the circulation becomes interrupted. If the blood 

 loses, by slow degrees, its stimulating qualities, the action of the heart 

 gradually weakened, impels towards the brain a blood which, by its 

 qualities, partakes of the nature of venous blood, and which, like it, 

 cannot preserve the natural economy of the brain. It was thought, that 

 by injecting a few bubbles of air into the jugular vein of a do.-, one might 

 occasion in the animal immediate syncope, and that it was even su.ncient 

 to deprive it of life; but the late experiments of Nysten have proved, 

 that the atmospherical air produces these bad effects, only when injected 

 in a quantity sufficient to distend, in excess, the cavities of the heart, or 

 when by being injected into the arteries it compresses the brain. When 

 injected only in a small quantity, the gas dissolved in the venous blood, 

 is conveyed along with it to the lungs, and is thence exhaled in respira- 

 tion. 



A second class of occasional causes consists of those which, by acting 

 on the epigastric centre, determine, by sympathy, a cessation of the pulsa- 

 tions of the heart and the syncope necessarily attending this sensation. 

 Such are the violent emotions of the soul, terror, an excess of joy, an ir- 

 resistible aversion to certain kinds of food, the dread which is felt on the 



