191 



the blood becomes very marked, however large may be the quantity of water 

 ingested. This is remarkably shown by the analyses of Lecanu, 1 who found 

 the proportion of solid constituents in some instances even to exceed that of the 

 water. 



Solid constituents . . 251 330 340 520 



Water 749 670 660 480 



No such degree of reduction has been observed by others ; still the general fact 

 is, that the proportion of water is considerably diminished. 



178. That the Blood is subject to a great variety of other morbid alterations, 

 which are sometimes the causes, and sometimes the results, of Disease, cannot 

 be for a moment doubted. But our knowledge of the nature of these changes 

 is as yet very insufficient. The great amount of attention which is being 

 directed by Chemical Pathologists to the subject, however, will doubtless ere 

 long produce some important results. Among the most frequent causes of de- 

 pravation in the character of this fluid, we must undoubtedly rank the retention, 

 in the Circulating current, of matters which ought to be removed by the Ex- 

 creting processes. We shall hereafter see, that a total interruption to the ex- 

 cretion of Carbonic Acid by the lungs, will occasion death in the course of a 

 very few minutes ; and even when only a slight impediment is oifered it, so that 

 the quantity of carbonic acid always contained in arterial blood is augmented 

 to but a small degree, a feeling of discomfort and oppression, increasing with 

 the duration of the interruption, is speedily produced. The results of the reten- 

 tion of the materials of the Biliary and Urinary excretions will be hereafter 

 considered (CHAP, xu.); and at present it will be only remarked that such 

 retention is a most fertile source of slight disorders of the system, that it is 

 largely concerned in producing many severe diseases, and that, if complete, it 

 will most certainly and rapidly bring about a fatal result. The most remarka- 

 ble cases of depravation of the Blood, by the introduction of matters from 

 without, are those in which these substances act as ferments, exciting such 

 Chemical changes in the constitution of the fluid that its whole character is 

 speedily changed, and its vital properties are altogether destroyed. Of such an 

 occurrence, we have characteristic examples in the severe forms of Typhoid 

 fever commonly termed malignant ; in Plague, Glanders, Pustule Maligne, 

 and several other diseases ; in some of which we can trace the direct introduction 

 of the poison into the blood, whilst in others we must infer (from the similarity 

 of result) that it has been introduced through some obscure channel, probably 

 the lungs. The evidence which we possess of the " intoxication" of the Blood, 

 in these and other cases, derived from the perversion of the nutritive operations 

 which it induces, will be considered in the next Section. 



3. Of the Vital Properties of the Blood, and its Relations to the Living 



Organism. 



179. It cannot be doubted that the perfect and regular performance of the 

 various actions to which the Blood is subservient, is dependent upon the admix- 

 ture of its principal components in their due proportions, and upon its freedom 

 from deleterious matters, whether formed within the system, or introduced into 

 the circulating current from without. And it is not difficult to see how any 

 considerable alteration which affects its physical conditions merely, may thereby 

 produce a most serious disturbance in the regularity of the circulation, and in 

 the functions to which it ministers. Thus it has been shown, by the experi- 

 ments of Poisseuille, that a certain degree of viscidity is favorable to the motion 



1 "Etudes Chimiques sur le Sang," p. 106. 



