ADULT CIRCULATION. 441 



sively from red to dark and from dark to red." This dif- 

 ference in color between the blood of the umbilical arteries 

 and of the umbilical vein has, however, been denied by some 

 authors, who state that all of the foetal blood, while it is of 

 nearly a uniform color, is lighter than the venous blood of 

 the adult ; * but Dalton, in a direct observation upon a cat, 

 " nearly arrived at the term of pregnancy," noted that " the 

 difference in color between the umbilical arteries and veins 

 was very distinct. They were both dark, but the color of the 

 veins was very decidedly more ruddy than that of the arte- 

 ries ; i. e., the blood in the umbilical arteries was of the color 

 of the ordinary venous blood, while that of the umbilical 

 veins had a color midway between the ordinary venous and 

 arterial hues. All the foetuses were healthy, and moved 

 briskly after being taken out of the uterus." 2 



There are numerous observations showing that the foetus 

 in utero makes respiratory efforts when the umbilical vessels 

 are compressed. 3 We believe that these, as well as the first 

 respiration after birth, are due to a want of oxygen in the 

 general system of the foetus, and think that we have demon- 

 strated this fact by experiments. This point has already 

 been elaborately discussed in another volume. 4 If our ex- 

 periments and the deductions drawn from them be correct, 

 there can be no doubt with regard to the respiratory func- 

 tion of the placenta, although, as far as we know, there has 

 never been an accurate comparison of the gases contained in 

 the blood of the umbilical arteries and the umbilical vein. 



The Third, or Adult Circulation. When the child is 

 born, the placental circulation is suddenly arrested. After a 



1 ROBIN, Lccons sur leshumeurs, Paris, 1867, p. 116. 



a DALTON, The Physiology of the Circulation. American Medical Monthly, 

 New York, November, 1860, p. 340. 



3 B. S. SCHULTZE, Der Scheintod Neugeborener, Jena, 1871, S. 64, et seq. 

 This is a very elaborate memoir, in which numerous references to experi- 

 ments are given. 



4 See vol. L, Respiration, p. 479, et seq. 



