ITS PHYSICAL, CHEMICAL, AND STRUCTURAL CHARACTERS. 259 



geu, the Blood appears to possess a, superior power of absorption than pure 

 water, 100 vol. of the latter absorbing at ordinary temperature and pressure 

 about 1.5 vol. of nitrogen, while 100 vol. of fresh defibrimited Blood de- 

 prived of gas by exhaustion will absorb about 5 vol. at a temperature of (i"> 

 F. and under a pressure of 0.6 m. (Setschenow). It is very evident then 

 that the absorption of these gases does not take place in accordance with the 

 ordinary law established by Dalton and Henry, but that chemical affinity 

 must come into play; and the investigations of Meyer, Fernet, Heidenhain, 1 

 Preyer, and Pfluger' 2 and others indicate that the carbonic acid present in 

 the "blood may be divided into two portions, of which one follows the ordi- 

 nary law of absorption, whilst the absorption of the other is only explicable 

 on the supposition of there being certain substances in the blood for which 

 it possesses a strong affinity, and with which it enters into combination. 

 These substances appear to be the carbonate and phosphate of soda con- 

 tained in the liquor sauguinis, for dilute solutions of both these salts in pure 

 water exert a well-marked influence in increasing the quantity of carbonic 

 acid which can be absorbed; in the former case a bicarbonate of the alkali 

 being formed, and in the latter case a peculiar double salt, represented, ac- 

 cording to Fernet, by the formula PO 4 + Na, + CO r 3 As regards the 

 Oxygen contained in the blood there seems every reason to believe that it 

 is chemically combined with the haemoglobin of the red corpuscles in which 

 it exists in the active or ozonized condition, and from which it can be ab- 

 stracted with the utmost facility by reducing agents, such as the sulphides 

 of potassium, ammonium, and hydrogen, protoxide of nitrogen, carbonic 

 oxide, and iron filings. The haemoglobin, therefore, plays a most important 

 part as a carrier of oxygen from the air to the tissues, the affinity of which 

 for ozone is still greater than that of haemoglobin. One gramme of haemo- 

 globin takes up from 1.2 to 1.3 c.c. of oxygen, carbonic oxide, and pro- 

 toxide of nitrogen at standard pressure and at C., but its affinity for pro- 

 toxide of nitrogen is stronger than for carbonic oxide, and for carbonic 

 oxide than for oxygen ; so that by presenting blood to these gases in that 

 order they may be made successively to replace each other. Carbonic oxide 

 is commonly employed as a means of determining the amount of oxygen 

 contained in blood, the coloring matter of which under its influence acquires 

 optical and other characters which remarkably resemble those of oxyhfe- 

 moglobiu. (3, Fig. 116.) The importance of the absorption of oxygen being 

 dependent upon chemical affinity and not simply upon pressure is sufficiently 

 obvious; since, by securing the introduction of a definite proportion of this 

 gas, it enables animal life to be maintained without difficulty at all alti- 

 tudes, and under the most various conditions of atmospheric pressure. 

 Preyer 4 states as the results of his experiments that Haemoglobin forms no 

 chemical compound with Carbonic Acid gas, nor does it materially alter 

 the capacity of water to absorb this gas. 



194. The actual quantity and relative proportions of the gases contained 

 in the blood, as well as the exact ratio of the combined to the simply ab- 

 sorbed gases, is still a matter of question. The following table gives the 

 most recent observations on this subject: 



1 Studien des Physiolog. Inst. zu Breslau, 1863, p. 103. 



2 Centralblatt f. d. Med. Wiss., 1867, Nos. 21 and 46. 



3 Heidenhain's experiments show that this statement only holds for very dilute 

 solutions. See Sertoli, Centralblatt f. d. Med. Wiss., 1868, No. 10. 



4 Die Blutcrystalle, 1871, p. 78. See also Claude Bernard, Le9ons, 1875. 



5 See Henle and Meissner, 1857, 1859, p. 303, 1860, p. 330; v. Gorup-Besanez, 

 Phys. Chemie, 1862, p. '62'2. 3Iathitni and L)'Urbain, Brown-Sequard's Archives, 1872. 



