TENSION OF THE GASES IN CAVITIES AND LYMPH. 



195 



Arterial blood. 

 Peritoneal cavity, 

 Acid urine, 



Mm. Mm. 



12*28 Hg tension. Bile, .... 50*0 Hg tension. 



58-5 Hydrocele fluid, . . 46*5 ,, 



68 "0 ,, ,, (Pflilger and Strassburg). 



The large amount of CO* in these fluids can only arise from the C0. 2 of the tissues passing into 

 them. 



Gases of Lymph. In the lymph of the ductus thoracicus the tension of C0 2 = 33*4 to 37*2 

 mm. Hg, which is greater than in arterial blood, but considerably less than in venous blood 

 (41 '0 mm. Hg). [Ludwig and Hammarsten, Tschirjeic] This does not entitle us to conclude 

 that in the tissues from which the lymph comes only a small quantity of C0 2 is formed, but 

 rather that in the lymph there is less attraction for the C0 2 formed in the tissues than in the 

 blood of the capillaries, where chemical forces are active in causing it to combine, or that in the 

 course of the long lymph-current, the C0 2 is partly given back to the tissues, or that C0 2 is 

 formed in the blood itself. Further, the muscles, which are by far the largest producers of C0 2 , 

 contain few lymphatics, nevertheless they supply much C0 2 to the blood. The amount of free 

 ** non-fixed" C0 2 contained in the juices and tissues indicates that the C0 2 passes from the 

 tissues into the blood ; still, Preyer believes that in venous blood CO undergoes chemical com- 

 bination. The exchange of and C0 2 varies much in the different tissues. The muscles are 

 the most important organs, for in their active condition they excrete a large amount Of C0 2 , 

 and use up much 0. The O is so rapidly used up by them that no free O can be pumped out 

 of muscular tissue (L. Hermann). The exchange of gases is more vigorous during the activity 

 of the tissues. Nor are the salivary glands, kidneys, and pancreas any exception, for although, 

 when these organs are actively secreting, the blood flows out of the dilated veins in a bright red 

 stream, still the relative diminution of C0 2 is more than compensated by the increased volume 

 of blood which passes through these organs. 



Reductions by the Tissues. The researches of Ehrlich have shown that in most tissues very 

 energetic reductions take place. If colouring-matters, such as alizarin blue, indophenol blue, 

 or methyl blue, be introduced into the blood-stream, the tissues are coloured by them. Those 

 tissues or organs which have a particular affinity for O (e.g., liver, cortex of the kidney, and 

 lungs), absorb O from these pigments, and render them colourless. The pancreas and sub- 

 maxillary gland scarcely reduce them at all. 



(2) In the blood itself, as in all tissues, O is used up and C0 2 is formed. 

 This is proved by the following facts : That blood withdrawn from the body 

 becomes poorer in O and richer in C0 2 ; that in the blood of asphyxia, free from 

 O, and in the blood-corpuscles, there are slight traces of reducing agents, which 

 become oxidised on the addition of O. Still, this process is comparatively insigni- 

 ficant as against that which occurs in all the other tissues. That the walls of the 

 vessels more especially the muscular fibres in the walls of the small arteries use 

 O and produce C0 2 is unquestionable, although the exchange is so slight that the 

 blood in its whole arterial course undergoes no visible change. 



Ludwig and his pupils have proved that C0 2 is. actually formed in the blood. If the easily 

 oxidisable lactate of soda be mixed with blood, and this blood be caused to circulate in an 

 excised but still living organ, such as a lung or kidney, more is used up and more C0 2 is 

 formed than in unmixed blood similarly transfused. 



(3) That the tissues of the living lungs use and give off C0 2 is probable. 

 When C. Ludwig and Muller passed arterial blood through the blood-vessels of a 

 lung deprived of air, the O was diminished and the C0 2 increased. As the total 

 amount of C0 2 and O found in the entire blood, at any one time, is only 4 

 grammes, and as the daily excretion of C0 2 = 900 grammes, and the O absorbed 

 daily = 744 grammes, it is clear that exchange of gases must go on with great 

 rapidity, that the O absorbed must be used quickly, and the C0 2 must be rapidly 

 excreted. 



Still, it is a striking fact that oxidation-processes of such magnitude, as e.g., the union of C 

 to form C0 2 , occur at the relatively low temperature of the blood and the tissues. It has been 

 surmised that the blood acts as an ozone -producer, and transfers this active form of O to the 

 tissues. Liebig showed that the alkaline reaction of most of the juices and tissues favours the 

 processes of oxidation. Numerous organic substances, which are not altered by O alone, 

 become rapidly oxidised in the presence of free alkalies, e.g., gallic acid, pyrogallic acid, and 

 sugar; while many organic acids, which are unaffected by ozone alone, are changed into 

 carbonates when in the form of alkaline salts (Gorup-Besanez) ; and, in the same way, when 

 they are introduced into the body in the form of acids, they are partly or wholly excreted in 



