74 PHYSIOLOGICAL CHEMISTRY. 



tainty in any case. Owing to the difficulty of obtaining them in a 

 state of absolute purity, the uncertainty whether their sulphur is an 

 essential constituent element or only an incidental ingredient, and par- 

 ticularly owing to the number and variety of the products of their artifi- 

 cial decomposition, their atomic constitution is still a matter of doubt. 

 The formula for albumen which was proposed by Lieberkiihn, and 

 adopted by Johnson and Schiitzenberger,* is as follows : 



Albumen; C 72 H 112 N 18 O 22 S. 



But although this formula has been shown to account in a satisfac- 

 tory manner for certain combinations and decompositions, it has not 

 been generally accepted ; and in the opinion of most chemists, the 

 manner in which the elements of these substances are combined is 

 entirely unknown. 



The albumenoid matters are not crystallizable. They always, when 

 pure, assume an amorphous condition, in which they are sometimes 

 solid, as in the bones ; sometimes fluid, as in the plasma of the blood ; 

 and sometimes semi-solid, as in the muscles and the glandular organs. 

 Even in the fluids, when present in considerable quantity, as in the 

 blood-plasma, the pancreatic juice, or the submaxillary saliva, they give 

 to the solution a viscid or mucilaginous consistency, which is more 

 marked in proportion to their abundance. 



Some of them are soluble in water, others in solutions of the neu- 

 tral salts in different degrees of concentration. Some of them may 

 be extracted from the solid tissues by water at a boiling temperature, 

 and a few resist the action of all solvent fluids. When in solution 

 they all rotate the plane of polarization toward the left. They are all 

 hygroscopic. When dried by evaporation, and afterward brought in 

 contact with water, they absorb it with readiness, becoming swollen 

 and assuming a more or less softened, gelatinous, mucous, or fluid con- 

 sistency, according to the quantity of water with which they were 

 originally associated. When subjected to artificial decomposition by 

 heat and a caustic alkali, they yield a great variety of gaseous and 

 crystalline substances, among which carbonic acid and ammonia are 

 constantly present in the proportion of 2 to l.f Oxalic acid and sul- 

 phurous acid are also given off as products of decomposition. 



The albumenoid substances are not diffusible; that is, they do not 

 readily pass, in solution, through parchment paper or animal mem- 

 branes. This character is probably connected with their amorphous 

 and uncrystallizable condition ; and they are distinguished by it in a 

 marked degree from mineral salts and crystallizable organic substances, 

 which pass through such membranes by diffusion with great facility. 

 It is frequently resorted to as a means for the purification of albume- 



* Wurtz. Chimie Biologique, Paris, 1880, pp. 65, 85. 



f Gorup-Besanez. Lehrbuch der Pliysiologischen Chemie, Braunschweig, 1878, 

 p. 114. 



