410 



BLOOD. 



jection of so much pure water, and death is 

 no less an inevitable consequence of the he- 

 morrhage. 



A variety of other experiments upon trans- 

 fusion, for which we are equally indebted to 

 Messrs. Prevostand Dumas, show the influence 

 which the form and volume of the globules of 

 the blood exert upon its physiological proper- 

 ties. If the blood introduced into the veins 

 of a living animal differs merely in the size, 

 not in the form of its globules, a disturbance 

 or derangement of the whole economy more or 

 less remarkable supervenes. The pulse is in- 

 creased in frequency, the temperature falls 

 rapidly, the alvine evacuations become slimy 

 and sanguinolent, and death in fine generally 

 happens after the lapse of a few days. The 

 effects produced by the injection of blood 

 having circular globules into the veins of an 

 animal the globules of whose blood are ellip- 

 tical, (or vice versa,} are still more remarkable ; 

 death then usually takes place amidst nervous 

 symptoms of extreme violence, and comparable 

 in their rapidity to those that follow the intro- 

 duction of the most energetic poisons. 



We know by observation and experiment 

 that it is the blood that supplies the living 

 tissues with the materials which they assimilate 

 to repair their losses resulting from the vari- 

 ous processes of which they are the seat, as 

 well as to add to their masses during the period 

 of their growth; thus, when by mechanical 

 means we lessen in a notable and permanent 

 manner the quantity of this fluid received by 

 any organ, we soon find it declining in size, 

 and often shrinking almost to nothing; whilst 

 on the other hand we see that the more blood 

 any part receives, the more does it tend to in- 

 crease in size. It has also been demonstrated 

 that it is at the expense of the blood that the 

 different glands prepare the fluids they are 

 destined to secrete, for the ligature of the ves- 

 sels which run to one of these organs is followed 

 by the immediate cessation of its secreting 

 function. From this it became an interesting 

 question to determine whether or not the blood 

 contains, ready formed, the various substances 

 of which these tissues and these secreted fluids 

 are composed, and if the organs it traverses 

 do anything more than merely separate these 

 from its mass, or whether the general nutrient 

 fluid only supplies to the different parts of the 

 economy the primary elements necessary to the 

 formation of the substances of which we have 

 spoken, which would then be originated by 

 the tissues or glands in which they are encoun- 

 tered. To resolve this question, it became 

 necessary to contrast the chemical composition 

 of the tissues and fluids of the economy with 

 that of the blood, and to ascertain whether the 

 last-named fluid contained all the variety of 

 substances which are met with elsewhere in the 

 animal organization. 



This very important part of organic chemistry 

 is not yet sufficiently advanced to enable us com- 

 pletely to answer the question : all we know, 

 however, goes to prove that the component 

 parts of the tissues and secreted fluids exist 



in the blood ready formed, and are only sepa- 

 rated from its general mass by the organs which 

 at first sight seem to produce them. In the 

 blood we discover 1st, water, an element 

 which enters in large proportion into the com- 

 position of all the fluids, and even forms a 

 considerable item in the constitution of all the 

 tissues : 2d, fibrine, which forms the basis 

 of the muscles : 3d, albumen, which is met 

 with in variable but still considerable quantities 

 in the brain, cellular substance, membranes 

 generally, and in the greater number of the 

 secreted fluids which are not excrementitious : 

 4th, a fatty phosporated matter, which enters 

 into the composition of the nervous system : 

 5th, a peculiar colouring matter of a yellow 

 hue, which, slightly modified, is perchance the 

 same as the pigmentum nigrum of the choroid 

 coat of the eye, and of melanosis : 6th, phos- 

 phate of lime and phosphate of magnesia, 

 salts which form the inorganic basis of the 

 bones : 7th, alkaline salts, which are met 

 with in almost all the fluids of the body : 8th, 

 cholesterine, a peculiar fatty matter existing 

 very abundantly in the bile : 9th, urea, a 

 substance characteristic of the urine : lastly, 

 various other matters more or less accurately 

 defined. 



Under ordinary circumstances our means of 

 analysis are inadequate to demonstrate the 

 presence of urea in the blood ; but if the ac- 

 tion of the organs destined to separate this 

 substance from its current in proportion as it is 

 formed, be arrested, the amount contained 

 goes on increasing continually, so that before 

 long it becomes easy to distinguish it. Messrs. 

 Prevost and Dumas have shown that, after the 

 extirpation of the kidneys, the blood always 

 contains urea in appreciable quantity.* This 

 experiment, the results of which have been 

 confirmed by Messrs. Vauquelin and Sega- 

 las, is of the highest importance, and shows 

 that if we have hitherto failed to discover 

 uric acid, caseum, and the other compo- 

 nent elements of the principal fluids in 

 the blood, we are not, therefore, to conclude 

 that they do not exist there; analogy would 

 even lead us to infer that they are actually 

 present, and that if we were to interrupt 

 the different glands in the performance of 

 their functions, they would be discovered 

 in appreciable quantity. Experiments con- 

 ducted in this view would be extremely in- 

 teresting. Another subject of inquiry, too, not 

 less important, would be to discover the source 

 of the gelatine which forms the basis of the 

 cartilages, tendons, ligaments, &c. and which 

 does not appear to exist in the blood. 



The most complete analysis of the human 

 blood we possess is that published lately by 

 M. Lecanu, a chemist of Paris.f The careful 

 examination of the blood of two strong and 

 healthy men afforded the following results. 



* Uilil. Univcrs. tie Geneve, and An. de Chemic, 

 2de Serio, t. xxiii. 



t Journal dc Phaiiii. No. ix. and x., 1831. 



