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COLLOIDS IN BIOLOGY AND MEDICINE 



(cholera), which result in dehydration of the entire organism. This 

 is combated by an injection of physiological salt solution into the 

 blood vessels. If, on account of abnormal conditions, there is an 

 increased swelling of tissue (edema, exudates), the balance may be re- 

 stored by withdrawing water from the blood (by sweating, diuretics 

 or cathartics). [Reference should be made to the influence exerted 

 by increasing the colloids of the blood either by transfusion of blood 

 or by injection of colloidal substances. Tr.] 



Respiration (Gas Exchange). 



The supply of oxygen to the cells is probably the most important 

 condition for the life of the organism, whether animal or plant. For the 

 latter, quantitative estimations are not as convenient, and on this ac- 

 count they have been less studied than in animals, especially mammals. 



In the case of higher animals, the provision of oxygen is assigned 

 to the red blood corpuscles which take up oxygen in the lungs or gills, 

 transport it to the places where it is needed, and return laden with 

 C02. Ability to take up and relinquish oxygen or carbon dioxid is a 

 characteristic of hemoglobin. Formerly, the combination of oxygen or 

 carbon dioxid and hemoglobin was considered to be a purely chemical 

 one. In favor of this view is the fact that it is possible to crystallize 

 both hemoglobin and also oxygen-laden oxyhemoglobin. The union 

 must be a very loose one, since it is possible to remove with an ex- 

 haust pump almost all the oxygen from an oxyhemoglobin solution or 

 even from oxyhemoglobin crystals, so that the absorption of oxygen 

 and carbon dioxid follows the gas pressure. It would be natural to 

 think of a solution of O or CO 2 in the hemoglobin, but quantitative 

 investigations show in contradiction that the absorption of O or CO 2 

 is not proportional to the outer gas pressure as would occur for the 

 solution of a gas in a fluid in accordance with Henry's law. It has 

 been found on the contrary, that with low gas pressures relatively 

 much or CO 2 is taken up, but that with higher pressures the amount 

 diminishes; the following table of A. LoEWY* 2 shows this: 



