Elements of chemistry : including the recent discoveries and doctrines of the science / by Edward Turner.

  • Turner, Edward, 1798-1837.
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Elements of chemistry : including the recent discoveries and doctrines of the science / by Edward Turner. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    853/948 (page 831)
    consumption of oxygen is unusually small, and the blood within the veins retains the arterial character. The connexion between the power of generating heat and respiration has been illustrated in a very pointed manner by Dr. Edwards. Some young animals, such as puppies and kittens, require so small a quantity of oxygen for supporting- life, that they may be deprived of that gas altogether for twenty minutes without material injury; and it is remarkable that so long as they possess this property, the temperature of their bodies sinks rapidly by free exposure to the air. But as they grow older they become able to maintain their own temperature, and at the same time their power to endure the privation of oxygen ceases. The same observation ap- plies to young sparrows, and other birds which are naked when hatched; while young partridges, which are both fledged and able to retain their own temperature at the period of quit- ting the shell, die when deprived of oxygen as rapidly as an adult bird. The first consistent theory of the production of animal heat was proposed by Dr. Crawford. This theory was founded on the assumption that the carbonic acid contained in the breath is generated in the lungs, and that its formation is accom- panied with disengagement of caloric. But since the tem- perature of the lungs is not higher than that of other internal organs, and arterial very little if at all warmer than venous blood, it follows that the greater part of the caloric, instead of becoming free, must in some way or other be rendered in- sensible. Accordingly, on comparing the specific caloric of arterial and venous blood, Dr. Crawford found the capacity of the former to exceed that of the latter in the ratio of 1030 to 892. He therefore inferred that the dark blood within the veins, at the moment of being arterialized, acquires an increase of insensible caloric; and that while circulating through the body, and gradually resuming the venous character, it suffers a diminution of capacity, and evolves a proportional degree of heat. Unfortunately for the hypothesis of Crawford, one of the leading facts en which it is founded has been called in question. Dr. Davy maintaining, on the authority of his own experi- ments, that there is little or no difference between the capa-