ALBUMEN. 339 



fore at best exhibit only a relative certainty, and this is specially 

 the case where we attempt to discover coagulated albumen; fortu- 

 nately, however, it rarely or never occurs in this condition in the 

 animal organism ; and from what has already been said (at p. 328) 

 in relation to the properties common to the coagulated protein- 

 compounds, it must be apparent that in the present state of science it 

 is useless to attempt drawing distinctions between them. Since the 

 determination of the atomic weight and the elementary analysis 

 are here unable to throw any light on the subject, we might be 

 disposed to take the quantity of sulphur contained in a substance 

 known to be a protein-compound (see p. 329) as a means of ascer- 

 taining its identity with coagulated albumen, fibrin, casein, &c., but 

 it unfortunately happens that the quantity of sulphur contained in 

 one and the same body, as for instance in albumen, is not constant. 

 We must for the present relinquish all hope of distinguishing from 

 one another the different coagulated protein-compounds of the 

 animal body, and hence it is utterly absurd to enquire whether it be 

 coagulated fibrin or albumen that exists in tubercles or in carci- 

 noma; and yet this is a point which many adherents of the 

 pathologico-anatomical school believe that they have satisfactorily 

 settled without the aid of chemistry. 



The method usually recommended for the quantitative determina- 

 tion of albumen in the animal fluids is simply to coagulate it by heat, 

 to collect it on a filter, and to dry and weigh it. At the first glance 

 this method seems to be highly practical, but as soon as we attempt 

 to prosecute it, we find our course impeded by unexpected diffi- 

 culties, unless we would rest content with such deficient and 

 inexact analyses as unfortunately are too common in pathological 

 chemistry. In the first place, it should be observed that the 

 albumen commonly contained in slightly alkaline animal fluids 

 cannot be regarded as capable of being collected on a filter after 

 its coagulation ; for while, on the one hand, some portion always 

 passes through the filter in consequence of its gelatinous or milky 

 character, the filter becomes on the other hand so quickly clogged 

 with the coagulated albumen as to preclude the possibility of 

 washing it out ; or the fluid passes so slowly through the filter, 

 that the albumen has time to putrefy. Those who suppose that 

 these evils can be remedied by the use of linen or woollen 

 materials as a filter, can have no idea of the degree of exactness 

 required in a chemical analysis; and we cannot refrain from 

 observing that the greater number of analyses of animal albumi- 

 minous fluids have been conducted in this manner, without any 



z 2 



