VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 743 



It may be recollected, that in a former part of this paper mention was made, that 

 tortoise-shell, horn, muscular fibre, and inspissated albumen, after long immersion 

 in very dilute nitric acid, and after being well washed, were soluble in boiling water; 

 and that a substance was formed, which, by becoming liquified when heated, by 

 being soluble in boiling water, by being precipitated by the tanning principle and 

 by nitro-muriate of tin, and lastly, by forming a gelatinous mass when the aqueous 

 solution was sufficiently evaporated and cooled, approached and resembled gelatin. 

 It would be perhaps too hasty to assert, that gelatin was thus absolutely formed ; 

 but if a substance so very similar to it could be thus produced, we may with some 

 reason conclude that the real gelatin, with its various modifications, is formed from 

 albumen, by the more efficacious and delicate operations of nature. 



In attempting to prove that albumen or the coagulating lymph is the original 

 animal substance, I have hitherto only stated chemical facts ; but when the phe- 

 nomena attending incubation are considered ; when the experiments made by emi 

 nent physiologists, such as Haller, Maitre Jean, and Malpighi, are viewed ; when 

 the oviparous foetus is seen to be progressively formed in and from the albumen of 

 the egg, so that, on the bursting of the shell which separated it from external 

 matter, the young animal comes forth complete in all its parts ; when such strong 

 facts as these are corroborated by those afforded by chemistry, it can scarcely be 

 doubted that albumen is the primary animal substance, from which the others are 

 derived ; and there is much cause to believe that the formation of gelatin, and of the 

 animal fibre especially, begins with the process of sanguification in the fcetus. 



As the 3 principal and essential component parts of the blood, viz. albumen, 

 gelatin, and fibre*, appear therefore to compose the various parts of animals, in 

 such a manner that one, being predominant, influences the nature of that part of 

 the animal which it is principally employed to form ; and as albumen, gelatin, and 

 fibre, by relative proportion, by the degrees of density, by the effects of organiza- 

 tion which singly or conjointly they have experienced, by the texture of the animal 

 substance which they, as materials and thus modified, have concurred to produce, 

 and by the proportion of natural or inherent moisture peculiar to each part of dif- 

 ferent animals, present an immense series of complicated causes ; so are the effects 

 found to be no less numerous and diversified, by the infinite variety in texture, 

 flexibility, elasticity, and the many other properties peculiar to the various parts 

 which compose the bodies of animals. 



* The whole of the blood, which by anatomists is divided into serum, red globules, and coagulating 

 lymph, when chemically examined, is found to consist of albumen, gelatin, and fibre. The serum 

 which remains liquid after the coagulation of the blood, is composed of albumen, gelatin, some saline 

 matter, and much water. The clot or crassamentum also affords, by repeated washing, a large pro- 

 portion of albumen and gelatin j after which a substance remains, in appearance very analogous to 

 muscular fibre, excepting that it is in a more attenuated state. This substance, called fibrin by chemists, 

 may be regarded as that part of the blood which has undergone the most complete animalization ; and 

 from which the muscular fibre and other organs of the body are formed. — Orig. 



