ABSORPTION. 307 



of an hour after being given on an empty stomach, lithium chloride may 

 be diffused into all the vascular textures of the body, and into some of 

 the non-vascular, as the cartilage of the hip-joint, as well as into the 

 aqueous humor of the eye. Into the outer part of the crystalline lens it 

 ^nay pass after a time, varying from half an hour to an hour and a half. 

 Lithium carbonate, when taken in five or ten-grain doses on an empty 

 stomach, may be detected in the urine in 5 or 10 minutes; or, if the 

 stomach be full at the time of taking the dose, in 20 minutes. It may 

 sometimes be detected in the urine, moreover, for six, seven, or eight 

 days. (Bence Jones.) 



Some experiments on the absorption of various mineral and vegetable 

 poisons, have brought to light the singular fact, that, in some cases, 

 absorption takes place more rapidly from the rectum than from the 

 stomach. Strychnia, for example, when in solution, produces its poison- 

 ous effects much more speedily when introduced into the rectum than 

 into the stomach. When introduced in the solid form, however, it is 

 absorbed more rapidly from the stomach than from the rectum, doubtless 

 because of the greater solvent property of t}ie secretion of the former than 

 of that of the latter. (Savory.) 



With regard to the degree of absorption by living blood-vessels, much 

 depends on the facility with which the substance to be absorbed can pene- 

 trate the membrane or tissue which lies between it and the blood-vessels. 

 Thus, absorption will hardly take place through the epidermis, but is 

 quick when the epidermis is removed, and the same vessels are covered 

 with only the surface of the cutis, or with granulations. In general, the 

 absorption through membranes is in an inverse proportion to the thick- 

 ness of their epithelia; so that the urinary bladder of a frog is traversed 

 in less than a second; and the absorption of poisons by the stomach or 

 lungs appears sometimes accomplished in an immeasurably small time. 



Conditions for Absorption. 1. The substance to be absorbed must, 

 as a general rule, be in the liquid or gaseous state, or, if a solid, must be 

 soluble in the fluids with which it is brought in contact. Hence the 

 marks of tattooing, and the discoloration produced by silver nitrate taken 

 internally, remain. Mercury may be absorbed even in the metallic state; 

 and in that state may pass into and remain in the blood-vessels, or be 

 deposited from them; and such substances as exceedingly finely-divided 

 charcoal, when taken into the alimentary canal, have been found in the 

 mesenteric veins; the insoluble materials of ointments may also be rubbed 

 into the blood-vessels; but there are no facts to determine how these 

 various substances effect their passage. Oil, minutely divided, as in an 

 emulsion, will pass slowly into blood-vessels, as it will through a filter 

 moistened with water; and, without doubt, fatty matters find their way 

 into the blood-vessels as well as the lymph-vessels of the intestinal canal, 

 although the latter seem to be specially intended for their absorption. 



