136 RESPIRATION 



fore no respiratory efforts take place. Respiratory movements occur, 

 however, even in very young foetuses, when there is a deficient supply 

 of oxygen. 



CUTANEOUS RESPIRATION 



Respiration by the skin, although important in many of the lower 

 orders of animals, is inconsiderable in the human subject and is even 

 more insignificant in animals covered with hair or feathers ; still, an appre- 

 ciable quantity of oxygen is absorbed by the skin of the human sub- 

 ject, and a quantity of carbon dioxide, which is relatively larger, is 

 exhaled. Carbon dioxide is given off with the general emanations from 

 the surface, being found, also, in solution in the urine and in most of 

 the secretions. 



An estimate of the extent of the cutaneous, as compared with pul- 

 monary respiration, has been made by Scharling, by comparing the 

 relative quantities of carbon dioxide exhaled in the twenty-four hours. 

 According to this observer, the skin performs -^ to ^ of the respiratory 

 office. It is difficult, however, to collect all the carbon dioxide given 

 off by the skin under normal conditions. In the observations by Aubert, 

 the estimate is much lower than that given by Scharling. 



ASPHYXIA 



A remarkable power of resisting asphyxia exists in newborn ani- 

 mals that have never breathed. Legallois found that young rabbits will 

 live for fifteen minutes deprived of air by submersion, but that this 

 power of resistance diminished rapidly with age. W. F. Edwards has 

 shown that there exists a great difference in this regard in different 

 species. Dogs and cats, which are born with the eyes shut and in 

 which there is at first a very small development of animal heat, will 

 show signs of life after submersion for more than half an hour ; while 

 Guinea pigs, which are born with the eyes open, are much more active 

 and produce a greater amount of heat, will not live for more than seven 

 minutes. The explanation of this is that in most warm-blooded animals, 

 during the first periods of extra-uterine life, the demands on the part of 

 the system for oxygen are comparatively slight. At this time there is 

 very little activity in the general processes of nutrition and in the con- 

 sumption of oxygen and the exhalation of carbon dioxide. The actual 

 difference between the consumption of oxygen immediately after birth 

 and at the age of a few days is sufficient to explain the remarkable 

 power of resisting asphyxia just after birth. 



Breathing in a Confined Space. An important question connected 

 with the physiology of asphyxia is the effect on the system of air vitiated 



