G. GENERAL NATURAL HISTORY AND ZOOLOGY. 285 

 CAUSES AND MECHANISM OP THE COAGULATION OF FLUIDS. 



Messrs. Matthieu and Urbain have recently made some 

 very important experiments upon the causes and mechanism 

 of the coagulation of fluids, particularly of the blood, which 

 they liken to a chemical precipitation. The transformation 

 of the soluble to an insoluble substance is produced by an 

 acid, whose eflect is generally counteracted by the alkalinities 

 of the fluid. The acid exists in none of the normal fluids of 

 the body except the blood. They make the following points 

 concerning it: 1. Carbonic acid is the agent in coagulating 

 the albumen. It only does this at an elevated temperature, 

 because of the ammoniacal salts which must be volatilized. 

 Cold albumen, if deprived of its ammonia, will be precipitated 

 by the acid. 2. Carbonic acid is also the cause of the coag- 

 ulation of fibrin, and blood deprived of it is incoagulable. 

 It can not produce this effect, however, normally, because it 

 is combined in the red globules which have a great affinity 

 for the gas. When the organs for its excretion, viz., the lungs 

 and the skin, do not perform their function, the acid accumu- 

 lates and produces intravascular coagulation ; as, for exam- 

 ple, in death by suffocation. By a similar accumulation be- 

 yond the limit of saturation of the blood-globules in the case 

 of ligature of a vessel coagulation is produced. Venous clots 

 are formed in the course of debilitatino; diseases because of a 

 degeneration of the red globules and loss of power to hold 

 the acid gas. 3. Cadaveric rigidity is produced by an ac- 

 cumulation in the muscles of this same agent, developed by 

 the slow oxidation of the tissues. 4. The coasjulation of milk 

 is preceded by analogous processes to those which induce 

 the muscular coagulation oi rigor mortis; in the former case, 

 however, lactic acid is produced, which coagulates the casein 

 at an. ordinary temperature. 



NATURE OF GASES DISCHARGED FROM THE STOMACH. 



The precise nature of the gases emitted by the mouth from 

 the stomach has not been well established, although the 

 occurrence of that of free hydrogen is shown by the fact 

 that they burn with a blue flame. Quite lately Ewald de- 

 scribed the case of a person suffering from chronic gastritis, 

 who, on lighting a cigar one day, was surprised to see this 



