ON THE DIGESTIVE ORGANS, AND THEIR APPENDAGES. 139 



within the substance of the muscles, and in the cellular interstices be- 

 tween them. Mercury, opium, arsenic, &c. affect the condition of a 

 living animal, if applied to the skin, or to the surface of a wound ; and the 

 bite of a venomous serpent is followed by death, from the absorp- 

 tion of the poison ; but, beyond this, the very particles composing the 

 body itself are all gradually and progressively absorbed. The emacia- 

 tion of illness is owing, in a great measure, to the action of the absorbent 

 system, which takes away more quickly than the secreting vessels de- 

 posit. All that is absorbed is thrown into the blood, and what is useless 

 is expelled the system, partly by exhalant vessels, in the form of vapour, 

 or perspiration, and partly by means of the kidneys, which separate 

 from the blood its excrementitious portion, whence, by a tube (the 

 ureter) from each kidney, it is conveyed into the urinary bladder (in 

 Mammalia), and finally discharged. 



Absorption takes place by means of a system of vessels, termed 

 the lymphatics, or lymph-carrying vessels ; their mouths, in the form 

 of pores, are universally spread over the surface of the body ; and 

 they are also multitudinous throughout its general structure. They unite 

 into large vessels, which ordinarily pass through glands, of which there 

 are several conspicuous groups in different parts of the body, and through 

 which the main lymphatic tubes take their course. In the neck, in the 

 axilla, and in the groin, these glands are very perceptible : whether 

 they are composed of cellular substance, or consist of a knot of lym- 

 phatic tubes, contorted and folded on each other, and surrounded by a 

 peculiar envelope, is not ascertained. Ultimately, the lymphatics merge 

 into the lacteal duct ; though it is asserted, by some anatomists, that 

 they communicate, in many places, immediately with the veins also ; 

 and this is very probable. Hence, by the nutritive vessels, or extreme 

 ramifications of the arterial system, on the one hand, and by the action of 

 the lymphatic system, on the other, the body is undergoing a perpetual 

 change. The use of food is to furnish to the blood a supply of nutritive 

 matter, in order that it may be ever prepared to meet the draught upon 

 its resources. 



It has been stated, that the chyle is conveyed with venous blood 

 to the right cavities of the heart ; from the right ventricle of the heart, 

 it passes, mingled with the blood, through the ramifications of the 

 pulmonary artery in the cellular tissue of the lungs : here the vital fluid 

 becomes arterialized, by the action of the oxygen of the air we breathe, 

 and is returned to the left side of the heart, by means of the pulmonary 

 veins, to be thence distributed, a life-sustaining stream, to every part of 

 the system. How erroneous are the common ideas of the solidity of 

 animal bodies ! the frames of the massive Elephant, the thick-set, heavy 

 Rhinoceros, the huge Whale, are composed of millions of tubes 



