48 MATERIAL COMPOSITION OF MAN. 



a. Albumen. This is one of the most common organic constituents; 

 and appears under two forms liquid and concrete. In its purest state, 

 the former is met with in white of egg whence its name ; in the serum 

 of the blood; the lymph of the absorbents; the serous fluid of the 

 great splanchnic cavities and of the areolar membrane; and in the 

 synovial secretion. It is colourless and transparent; without smell or 

 taste ; and is coagulated by acids, alcohol, ether, metallic solutions, 

 infusion of galls, and by a temperature of 158 Fahrenheit. A very 

 dilute solution, however, does not become turbid until it is boiled. It 

 is excreted by the kidneys in large quantities, in the disease, which, 

 owing to its presence in the urine, has been called Albuminuria. 



Concrete, coagulated, or solid albumen, is white; tasteless; and elastic; 

 insoluble in water, alcohol, or oil ; but readily soluble in alkalies. 



Albumen is always combined with soda. It exists, in abundance 

 both the liquid and concrete in different parts of the animal body. 

 Hair, nails, and horn consist of it ; and it is, in some form or other, a 

 constituent of many tumours. 



In the advanced chyliferous vessels albumen is found in quantity; 

 and it is probable, that every proteinaceous aliment, and perhaps those 

 that are not proteinaceous, is reduced to the form of albumen in the 

 process of digestion, so that it becomes the nutritious constituent of 

 whatever fluid is absorbed for the formation of tissue. It is not, of 

 itself, organizable ; requiring first to be converted into fibrin. 



b. Fibrin. This proximate principle exists in the chyle ; enters into 

 the composition of the blood ; forms the chief part of muscular flesh ; 

 and may be looked upon as one of the most abundant animal substances. 

 It is obtained by beating the blood with a rod, as it issues from a vein. 

 The fibrin attaches itself to each twig in the form of red filaments, 

 which may be deprived of their colour by repeated washing with cold 

 water. Fibrin is solid ; white ; flexible ; slightly elastic ; insipid ; in- 

 odorous ; and heavier than water. It is neither soluble in water, alco- 

 hol, nor acids ; dissolves in liquid potassa or soda, in the cold, without 

 much change ; and when warm, becomes decomposed. 



Fibrin constitutes the buffy coat of blood; it is thrown out from the 

 blood-vessels, as a secretion, in many cases of inflammation; and be- 

 comes subsequently organized. 



There iswo mode of distinguishing liquid fibrin from liquid albumen, 

 except by the spontaneous coagulation of the former. Consequently, 

 according to Henle, 1 if a liquid does not coagulate of itself, it does not 

 contain fibrin. A very small quantity, however, of fibrin may be so 

 dissolved in serous fluid, that it will not coagulate. 2 The change of 

 albumen to fibrin has been regarded as the first important step in the 

 process of assimilation, fibrin being endowed with much higher organ- 

 izable properties than albumen. This has been attributed to some 

 influence exerted upon albuminous fluids by the living surfaces over 

 which they pass. 



The correspondence of fibrin with albumen is shown by the circum- 



1 Op. cit., p. 38. 



3 Dr. Buchanan, Lond. Med. Gaz. for 1836, pp. 52 and 90, and ibid, for 1845, p. 617. 



