148 



THE BLOOD 



The antitoxins and agglutinins in the blood seem either to be associated 

 with, or actually are a portion of, the para- or pseudoglobulin. During im- 

 munization, the pseudoglobulin of the blood may be twice the normal con- 

 tent; coincidently the per cent, of the serumalbumin will diminish. The 

 protein changes in the blood of horses and the antitoxic variations, how- 

 ever, are not parallel, and no quantitative relationship has been established. 



PHYSICAL FACTORS OF BLOOD PLASMA OR SERUM. 



Diffusion, Osmosis, Dialysis. The term diffusion has long been ap- 

 plied to the regular mixing of the molecules of two gases when brought 

 into contact in a confined space, this interpenetration being due to the 

 to-and-fro movements of their molecules. More recently it has been 

 applied to the mixing of the molecules of two solutions when brought into 

 contact, as it has been found that they act in the same way and obey the 

 same laws as gases. If, however, the two solutions are separated by a 

 membrane, permeable to the solutions, diffusion will still occur. To this 

 form of diffusion the term osmosis has been applied in the case of water, 

 and dialysis in the case of diffusible substances. All bodies can be 

 divided into two groups, crystalloids and colloids. To the former group 

 belong bodies having a crystalline form, which readily go into solution 

 in water. All such bodies are diffusible (dialyzable), their power of 

 dialysis, however, varying considerably. To the second group belong 

 such bodies as have no crystalline form (amorphous). These are generally 

 bodies with a large molecule, which form colloidal suspensions in water and 

 are only slightly or not at all diffusible. An exception 

 to this second group is hemoglobin, which has a very 

 large molecule, but is crystalline and is diffusible. \ T 



The following may serve as simple illustrations: 



Take a jar and divide it in two equal parts by an 

 animal membrane, M, figure 124, and place an equal 

 amount of distilled water in the two sides, A and B. 



FIG. 124. 



FIG. 125. 



