266 TENSION OF THE GASES IN CAVITIES AND LYMPH. 



Pfluger and Strassburger found the tension of C0 2 to be, in 



Mm, 



Arterial blood, . 21 -28 Hg. tension. 

 Peritoneal cavity, 58 '5 ,, ,, 

 Acid urine, . 68*0 ,, ,, 



Mm. 



Bile, . . . 50'0 Hg. tension. 

 Hydrocele fluid, . 46'5 ,, ,, 



The large amount of C0 2 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 thoraciciis the tension of 

 C0 2 = 33'4 to 37 '2 mm. Hg., which is greater than in arterial blood, but consider- 

 ably less than in venous blood (41 '0 mm. Hg). This does not entitle us to 

 conclude that hi the tissues from which the lymph comes, only a small quantity of 

 C02 is formed, but rather that in the lymph there is less attraction for the COs 

 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 , con- 

 tain 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 indi- 

 cates that the C0 2 passes from the tissues into the blood; still, Preyer believes that 

 in venous blood C0 2 undergoes chemical combination. 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 O. The 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. 



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

 formed. This is proved by the following facts : That blood with- 

 drawn from the body becomes poorer in and richer in C0 2 ; that in 

 the blood of asphyxia, free from 0, and in the blood-corpuscles 

 (Afanassieff), there are slight traces of reducing agents, which become 

 oxidised on the addition of (A. Schmidt). Still, this process is 

 comparatively insignificant 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 and produce C0 2 is 

 unquestionable, although it 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 Miiller passed arterial blood through 

 the blood-vessels of a lung deprived of air, the was diminished and 

 the CO., increased. 



