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 skew 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.
The specific gravity of morbid serum has been much oftener ascertained than that of morbid blood, and it leads to more precise information. The normal proportion of salts does not raise the specific gravity of serum above that of distilled water more than five parts in 1000.* The excess beyond this increase is owing to the presence of albumen. The quan tity of other animal matter is too small to be worth taking into the account. Hence the spe cific gravity of serum indicates with tolerable accuracy the quantity of albumen it contains.
In some states of disease, where albumen is rapidly carried out of the system, as in dis eased kidneys, in dropsies, and in profuse haemorrhages, the specific gravity of serum has been observed as low as whilst in other states, where water and even salts are removed, as in cholera, it is found as high as 1.041.1 Neither the specific gravity of fibrine nor of red particles has been hitherto stated by authors. The former, by immersion in solution of salt, I find to be at 60° Fahrenheit. Some of the latter will fall to the bottom of a solution of specific gravity 1•29, and when agitated with a solution of even specific gravity 1.207, which is the point of saturation, will not rise to the top ; but the experiment is not con clusive, for the red particles certainly undergo some change by the addition of salt in solution.
The temperature of the blood is materially influenced by disease. In fevers it is generally though not always above the healthy standard. In the cold stage of an intermittent the tempe rature of the skin has, according to Dr. Wilson Philip, been observed as low as 74° Fahren heit, while in its hot stage it has increased to 105°. A corresponding diminution or increase
in the temperature of the blood in all probability occurred in these cases. Ilaller cites authorities to prove that in pleurisy and yellow fever the temperature ature of the blood has been known to rise to 102° and in intermittent fever to 106° and 1080, and in continued fever to 109°. Mor gagni devotes several pages to the.history of a woman, as related in the journal of a cotempo rary, Media Via, whose blood flowed in an icy cold state from the arm. The serum of this blood was in small proportion and of a yellow colour • the crassamentum black and viscid. This person seems to have undergone repeated venesection, Thackrah witnessed similar phenomenon.
Whatever theory may be adopted respecting the generation of animal heat, it is a fact which is generally admitted, that it is effected through the medium of the blood, that it is, ceteris paribus, increased in proportion to the velocity, freedom, and force of the circulation, and that it is mainly dependent for its development upon the presence of the red particles. Wherever these are deficient, either from natural disease or artificial depletion, animal heat is deficient likewise. Chlorotic females and those who are subject to habitual losses of blood usually suffer from coldness of the extremities. The phenomenon of fainting is always accompanied by diminished temperature ; and whenever we cut off the supply of blood from a limb, it loses its natural warmth as an immediate conse quence. Plethoric subjects, on the contrary, provided their circulation be unimpeded at its capillary extremities, or in the process of the pulmonary ventilation, are liable to preter natural heat of the surface and profuse perspi ration. As an actual diminution or increase in the quantity of the red particles produces a corresponding increase or diminution of animal heat, notwithstanding the natural change of venous to arterial blood, so likewise any cause which impedes that change, although the red particles be not deficient in quantity,will produce a like effect. Thus, in diseases of the heart, in pulmonary obstructions, especially of a spas modic character, in the cold fit of ague, and in Asiatic cholera, there is a of the natural warmth, although there is no reason to suppose that the red particles are actually less abundant than in health.