186 ANATOMY AND PHYSIOLOGY. 



a few pounds. The conditions which promote the one generally 

 impede the other. When the body is saturated with fluid, absorp- 

 tion goes on slowly ; but exhalation, under the same circumstances, 

 takes place rapidly. M. Majendie found that when a quantity of 

 water was thrown into an animal's veins, absorption was either 

 much impeded, or altogether suspended ; and, on the other hand, 

 when the blood-vessels were partly emptied by bleeding, the effects 

 of a poison, that usually showed themselves at the end of the 

 second minute, were distinctly perceived before the thirtieth second. 

 A frog, kept for some time previously in dry air, when its legs are 

 immersed in water, will in a short time absorb nearly its own weight 

 of the fluid. 



We have already spoken of the absorbing powers of the intes- 

 tinal canal. The next in importance, as an absorbing surface for 

 external substances, is the lungs, and, of course, the matters ab- 

 sorbed are generally conveyed in the form of vapor. When a fluid 

 poison, however, is injected into the windpipe, it acts with fearful 

 rapidity. It is through this surface that substances diffused in the 

 atmosphere usually produce their effects on the system. The vapor 

 of turpentine, breathed along with the air of a room, may be de- 

 tected in the urine within a short time afterwards, and the concen- 

 trated vapor of such poisons as prussic acid will instantly kill an 

 animal if inhaled. The various poisons which produce fever, 

 measles, small-pox, and other infectious disorders, are in this way 

 introduced into the body, the smallest quantity frequently sufficing 

 for this purpose. We can conceive the small quantity of the poison 

 required, when we notice that the least particle of the matter of the 

 small-pox ? placed in a scratch on the skin, gives rise to the same 

 disease. In proof of the action of poisons, when inhaled by the 

 lungs, the following facts may be stated. 



M. Majendie contrived some experiments, in which dogs were 

 confined in the upper part of a barrel, the lower part being filled 

 with putrifying animal substances, which were separated from the 

 dogs by a grating. Confinement in this situation, from the absorp- 

 tion of the putrid effluvia, produced death generally about the tenth 

 day. The animals took food, and were even lively, but became 

 much emaciated before death. The same physiologist produced 

 symptoms exactly resembling those of yellow fever, by injecting a 

 few drops of putrid water into the veins of dogs. 



A nurse in one of the Dublin hospitals, apparently in excellent 

 health, was desired by the physician to assist a patient, laboring 



