GENERAL CONSIDERATIONS. 155 



uninjured peritoneal cavity, or when directly thrown into the blood. There may 

 be here also a question of temperature and other conditions. 



The following facts as elicited in these investigations seem to be sufficient to 

 explain the mechanism of the hemorrhages: the blood pressure has been shown 

 to play a most important part; a watery salt solution substituted for the blood does 

 not extravasate, hence, blood seems to be necessary ; there always occur molecular 

 changes in the bloodvessel walls from the effect of venom. That blood pressure is an 

 important factor has been established by the observation that the hemorrhages as a 

 rule occur first in the capillaries which are immediately next to or nearest the large 

 bloodvessels. The hemorrhages take place soonest where the force of the blood 

 current is first felt and cannot be sufficiently resisted, and in no case do hemor- 

 rhages seem to originate from vessels with strong walls like the arterioles or veins. 

 Cutting off the circulation of a part, as, for instance, by ligation of the vessels of 

 the mesentery, destroys the blood pressure, and, as a consequence, the hemorrhages 

 are so slight as scarcely to be seen by the naked eye though venom was freely 

 applied. Finally, the colloid, softened, diffluent condition of the red corpuscles 

 must inevitably facilitate extravasations. It is impossible to have seen numerous 

 cases of venom poisoning without noting a variety of symptoms often abrupt or 

 unexpected. These often are due, as Dr. Mitchell long since pointed out, to acci- 

 dental hemorrhages into brain, kidney, and heart tissues. They explain much 

 which might otherwise seem inscrutable, and serve sometimes to give a marked 

 individuality of symptoms to cases which survive long. 



10. Among the most remarkable effects of venom is that upon the red blood- 

 corpuscles. These bodies undergo substantial modifications, i. e., they lose their 

 bi-concave shape, become spherical and softened, and fuse together into irregular 

 masses acting like soft elastic colloid material. This jelly-like condition of the 

 corpuscles is no doubt doubly important: in connection with the extravasation of 

 the blood, and in its probable interference with the normal respiratory functions of 

 the blood-cells. 



11. The direct action of venom upon the nervous system save as concerns the 

 paralysis of the respiratory centres is of but little importance. 



12. The alterations in the pulse-rate are dependent chiefly upon two antagonistic 

 factors which are active at the same time, the one tending to increase the rate and 

 the other to diminish it. The former is found in the increased activity of the 

 accelerator centres and the other in a direct action on the heart. When we have the 

 action on the accelerator centres removed by isolation of the heart from any centric 

 influence we almost invariably find a diminution of the heart beats. Occasionally 

 after this operation the pulsations are increased, but this alteration is attended, as 

 in the case of the diminution of the pulse, by feeble heart beats, and accordingly 

 is but a manifestation in another way of a depressed condition of the heart. 



13. The variations in arterial pressure are due chiefly to three causes, depression 

 of the vaso-motor centres, depression of the heart, and irritation and consequent 

 constriction or blocking up of the capillaries. It seems not improbable that all of 

 these are consentaneously active, and it therefore follows that such alterations are de- 

 pendent upon the relative degree of power exerted by any one of these factors. Our 



