BLOOD, MORBID CONDITIONS OF THE. 



41? 



hours' rest, as 1000 to 1323. The specific gra- 

 vity of the crassamentum was 1'083. 



The lightest blood which I have met with 

 was of specific gravity 1-031, at 90 Fahren- 

 heit. It was taken from the arm of a female, 

 aged 22, who was bled on account of headach, 

 and had a full pulse of 117. 



The red particles being the heaviest of all 

 the constituents of the blood, their relative 

 quantity must greatly affect its specific gravity; 

 and as Messrs. Prevost and Dumas have shewn 

 that they bear a general proportion to the de- 

 gree of animal heat, we might reasonably sup- 

 pose that, ctfteris paribus, the heaviest blood 

 would be found in those diseases which are 

 marked by high action and increased tempera- 

 ment. In a fluid so complicated, however, in 

 which every constituent is liable to such variety 

 in quantity, it is difficult to estimate the precise 

 influence of each. I am not aware that any 

 experiments have been made on this subject. 



Blood diminishes in specific gravity in pro- 

 portion to its frequent abstraction, for the red 

 particles and the fibrine are reproduced with 

 more difficulty than the serum or the salts. The 

 serum also becomes lighter from a gradual di- 

 minution of its solid contents. A recent paper 

 by Mr. Andrews, in the fifteenth volume of the 

 Medical Gazette, p. 592, proves these facts very 

 satisfactorily by experiments made on calves. 

 They have, however, been long known. 



The specific gravity of morbid blood, says 

 Thackrah, differs little from that of healthy 

 blood ; but this observation is only true of an 

 average deduced from numerous specimens of 

 blood examined under different forms of dis- 

 ease. It would be equally true, perhaps, 

 according to the same mode of obtaining a 

 result, were we to affirm that the temperature 

 of the body or the state of the pulse differed 

 little in health and disease, since there might 

 be as many instances of deficiency as of ex- 

 cess in heat or action. The assertion is not 

 applicable to particular cases, and is, therefore, 

 without value. Blood may be morbid from 

 an undue proportion of any of its constituents, 

 and it will be heavier or lighter than healthy 

 blood according to the preponderance of the 

 heavier or lighter principles. Where the spe- 

 cific weight is increased, it is generally owing 

 to a deficiency in the proportion of water, as in 

 the blood of cholera and diabetes ; sometimes 

 to an increase of fibrine and red particles, as in 

 plethora, gout, and rheumatism. 



The following table, containing the specific 

 gravities of blood under several forms of dis- 

 ease, is compiled from a few cases of my own 

 which were recorded for another purpose. 

 Though short, it will be sufficient to shew that 

 considerable variety occurs, and may collaterally 

 suggest that in determining the propriety of de- 

 pletion, it may in some cases become impor- 

 tant thus to ascertain the proportion of solid 

 matter existing in the circulation. A specific 

 gravity bottle, holding 1000 grains of distilled 

 water, was employed in all the experiments, so 

 that the proportion of serum to clot was not 

 influenced by variation in the shape or material 

 of the receiver. 



VOL. i. 





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