324 PULMONARY MUCOUS TISSUE. 



it is to be expelled. In the foetus this intermediary function 

 is twofold : the blood of the foetus does not make the ex- 

 changes directly with the exterior air; it receives oxygen, 

 and gives out carbonic acid, only indirectly, through the 

 blood of the mother ; it has, by means of the placenta, one 

 more station of transit between the tissues and the exterior 

 air than in the adult life. The means by which the elements 

 of the blood serve as the vehicle for oxygen and carbonic 

 acid has already been sufficiently indicated in our preceding 

 study (red globules of the blood and their hemato-crystalline ; 

 the serum and its salts, see pp. 12'2 and 130). 



The perfect condition of the blood globule, which indicates 

 the capacity of the blood to absorb oxygen, thus has an effect 

 on the phenomena of oxidation ; and the products of combus- 

 tion, therefore, vary in quality, and even in quantity, in a 

 corresponding manner. This Ritter especially sought to 

 decide by studying the chemical modifications through which 

 the secretions pass when under the influence of agents which 

 augment, annihilate, or modify the capacity of the globule for 

 the absorption of oxygen. He studied the effect produced 

 by the following compounds: oxygen, protoxide of nitrogen^ 

 oxide of carbon, compounds of antimony and arsenic, phos- 

 phorus and the salts of soda, and the acids of the bile. These 

 substances are divided into two classes, according to their 

 action on the blood globule : the Krst includes oxygen, the 

 protoxide of nitrogen, and the oxide of carbon. These three 

 agents do not destroy the form of the globule ; it is never 

 dissolved under their influence, nor does it form any hemo- 

 globine crystals. The second class, on the other hand, con- 

 sists of substances which, whether the quantity be large or 

 small, materially alter the shape of the globule, and give rise 

 to the appearance in the blood of the animal of the crystals 

 which are the distinguishing sign of hemoglobine. The com- 

 position of the urine is connected with the perfect physiolo- 

 gical condition of the blood globule. When any serious 

 change occurs in the blood globule, and especially when the 

 crystals of hemoglobine appear, the urine is found to contain 

 abnormal principles, which are usually the coloring matters 

 of the bile and albumen. Under these circumstances the 

 urine resembles that observed in a fever. 1 



1 Ritter, " Des Modifications Chimiques que subissent les Sd- 

 crctions sous Plnfluence de quelques Agents qui inodifient lea 

 Globules Sanguins." Paris, 1872. 



