334 PULMONARY MUCOUS TISSUE. 



this fact is connected with the phenomena of development 

 and increase of active life belonging to the child. One of the 

 most curious of the conditions affecting the quantity of car- 

 bonic acid exhaled in respiration, is the influence of sex, and 

 of menstruation in women. The researches of Andral and 

 Gavarret show that the quantity of carbonic acid exhaled by 

 man increases until the age of thirty years, and after that 

 period diminishes. In woman, the quantity of carbon ex- 

 haled increases up to the period of puberty, until the appear- 

 ance of the first catamenial discharge: from this time it 

 remains stationary, until the menopause increases it for a 

 short time, after which it follows the same downward course 

 as in an old man. This is, no doubt, because at each cata- 

 menial period a considerable quantity of material flows from 

 the economy with the blood. This material is not subjected 

 to the action of the oxygen, but the products of their imper- 

 fect combustion are not eliminated with the gaseous ex- 

 changes of respiration ; thus, during pregnancy, the menses 

 being suppressed, the quantity of carbon exhaled by the 

 respiratory organs is considerably increased, diminishing as 

 menstruation returns. 1 



The mean result of respiration is as follows : an adult man 

 excretes 850 grnis. of carbonic acid (see p. 317) in 24 hours, 

 forming a volume of about 400 litres. A knowledge of this 

 figure is of practical use, inasmuch as it shows how much 

 pure air is required by an adult man of average vigor. A 

 proportion of jTyW f carbonic acid in the air inhaled is 

 admitted to be injurious. Now, if we give out 400 litres of 

 carbonic acid in 24 hours, 16 litres will be got rid of in an 

 hour, which is exactly sufficient to vitiate 4 cubic metres 



(the proportion being |^. Paul Bert). By means of this dis- 

 covery Paul Bert explains the resistance to asphyxia in new-born 

 animals. It is a well-known fact that a dog, just born, may be 

 immersed in tepid water for half an hour, and yet be taken out 

 alive; and it will resist strangulation, or copious bleeding, etc., for 

 a much longer space of time. This circumstance can only be ex- 

 plained by supposing that its circulation still resembles that of its 

 foetal existence, as the same state of things continues even when 

 the amount of blood has been diminished by long-continued bleed- 

 ing. The resistance of the newly born animal can be explained 

 only by the fact of a still greater resistance on the part of its ana- 

 tomical elements, which, consuming less oxygen, can therefore 

 longer support the want of it. 



1 Andral et Gavarret, " Recherches sur la Quantite d'Acide 

 Carbonique exhale par le Poumon dans 1'Espece Humaine." 

 (Annal. de Chimie et de Physique. 1843.) 



