1 6 INTRODUCTION. 



Name. Where Found. 



5C . f Hematine 1 f Coloring Matter of Blood. 



| Metoine All contain Iron. *"igmcnt 



o Biliverdine f Bile. 



[Urrosacine j [ " " Urine. 



Fibrin. 



Fibrin is found in the blood, lymph, and chyle. In 

 the first-named fluid it exists in considerable quantity, but 

 in the last two it is much less abundant. Its quantity has 

 been estimated by chemists in all the above-mentioned fluids, 

 but the analyses which are generally given represent dried 

 fibrin, and give us no definite idea of its quantity in the form 

 in which it naturally exists. The quantity of fibrin in the 

 blood, estimated by the author by a process in which it is 

 not exposed to desiccation, is between 8 and 9 parts per 

 1000. 1 This proportion is undoubtedly quite variable within 

 the limits of health. According to Becquerel and Rodier, 2 its 

 quantity is considerably increased during gestation, and is 

 greater in adults than in very young or very old persons. 

 As a general rule, it is more abundant in arterial than in 

 venous blood, and is often entirely absent from the blood of the 

 hepatic and renal veins. No constant diiference in quantity 

 has been established in the sexes, and its proportion appears 

 to bear no definite relation to the vigor of the individual. 



It appears in the blood at about the fifteenth day of intra- 

 uterine life, and exists constantly from that time. 



The composition of fibrin is given in the table. It con- 

 tains carbon, hydrogen, oxygen, nitrogen, and a little sulphur. 

 The proportion of these substances, however, is indefinite, 

 and the formula, like that of all the principles of this class, 

 is entirely arbitrary, as it enters into no definite combina- 

 tions, and consequently has no combining equivalent. Its 

 ultimate composition is comparatively unimportant, for it 



1 See article in Am, Jour., loc. dt. Though the ordinary methods of analysis 

 do not give the real quantities of fibrin, they give important results with regard to 

 the comparative quantities in different situations. 



2 BECQUEREL and RODIER, Traite de Chimie Pathologique, p. 101 ct scq. 



