146 THE BLOOD. 



Chevreul, Lassaigne, and others discover a yellow colouring 

 matter like that of the bile and urine. Dumas and Prevost and 

 others discern something like urea, which M. Raspail suggests 

 may be the effect of their experiments, as Woehler discovers urea 

 to be a cyanite of ammonia, and capable of artificial produc- 

 tion by passing cyanogen (bicarburet of nitrogen) through am- 

 moniacal gas. > 



" The serum is a peculiar fluid, the chief cause of the viscidity 

 of the blood, and easily separable by art into different constituent 

 principles. If subjected to a temperature of 150 Fahr., a por- 

 tion is converted into a white scissile substance, resembling 

 boiled white of egg," and is in truth albumen; the watery por- 

 tion which remains was termed serosity by Cullen, and contains 

 various substances. 



If mixed with six parts of cold water, serum does not coagulate 

 by heat. 



Under the influence of the galvanic pile, soda collects at the 

 negative wire, and the albumen coagulates at the positive, on 

 account, M. Raspail says, probably, of the decomposition of the 

 salts and also of the water, and the consequent oxygenation of 

 every thing at the positive pole, where the oxygen collects ; and 



small dog, with only temporary inconvenience, and subsequently three drams of 

 expired air even without much temporary disturbance. (Med. C/iir. Trans. 1818, 

 p. 65. sq.) Nysten has established that many gases soluble in the blood, as 

 oxygen and and carbonic acid, may be thrown into the circulating system in very 

 large quantity without serious inconvenience ; while danger often ensues upon 

 the introduction of those which are sparingly or not at all soluble in the blood. 

 (Magendie, 1. c.) 



In the same way, if about 15 grains of bile are rapidly introduced into the 

 crural vein of an animal, instant death occurs ; but, if slowly, no inconvenience 

 results. This quantity may be even rapidly injected into the vena portee without 

 injury, and so likewise may atmospheric air, probably because the extreme sub- 

 division of the vessel acts like slowness of introduction, causes the complete 

 diffusion and dilution of the bile, and solution of the air, before it reaches the 

 heart. 



If warm water is introduced (an equal quantity of blood being first removed, 

 to prevent over distension) mere debility ensues, proportionate to the quantity ; 

 but if oils, or mucilages, or an inert impalpable powder, are injected, life is at 

 once destroyed by the obstruction of the minute ramifications of the pulmonary 

 artery. (Magendie, Journal de Physiologic, t, i., and 1. c. t. ii. p. 260.) Poisons 

 act powerfully if injected into the veins ; and, as will presently be mentioned, 

 medicines, thus introduced, exert their specific powers on the different organs. 



