1869.] Dr. Norris on the Aggregation of Blood-corpuscles. 433 



each other, it is found that the moment any point in their convex surfaces is 

 made to touch, these surfaces become flattened, and consequently bubbles 

 in a group convert each other into polyhedral- shaped bodies. This effect 

 is not due to compression, but to a progressive mutual attraction of the 

 surfaces of these bodies for each other. 



As soap-bubbles are vesicles with aerial contents, and are therefore 

 physically unlike the blood-corpuscles, it became desirable to ascertain how 

 vesicles with liquid contents would behave in regard to each other. This 

 was accomplished by placing in a large test-tube a solution of soap, and 

 upon its surface a stratum of petroleum an inch or so in depth ; the petro- 

 leum does not mix with or injure the soap solution, which is the case with 

 most other substances. A glass tube is now passed through the petroleum 

 into the solution of soap below. On blowing down the tube, we succeed in 

 forming innumerable small bodies or corpuscles of a spherical form, which 

 are very plastic, and the contents of which consist of petroleum, and the ex- 

 ternal envelope or vesicle of soap. Corpuscles so produced float in the upper 

 stratum of petroleum, and are found to unite themselves into groups and 

 masses in precisely the manner of the air-bubbles, although they are en- 

 tirely submerged in liquid. 



These experiments show that disk-shaped bodies, having an attraction 

 for each other, will arrange themselves in rolls or cylindrical masses, and 

 that spherical bodies of a plastic character and vesicular structure, be their 

 contents aerial or liquid, will attach themselves together in such a fashion 

 as to cause plane surfaces to be opposed to each other — in a word, convert 

 themselves by a progressive attraction, which commences at their points of 

 mutual contact, into groups of polyhedral bodies. 



The question now remaining is, do the blood-corpuscles possess such 

 attractions for each other as those displayed by the objects with which we 

 have been dealing ? The reply is that their physical nature being analo- 

 gous, if the same conditions exist, they cannot escape the influence of the 

 same law. An examination of the photographs and of the drawings of 

 blood-corpuscles exhibited will serve to show that these bodies are amenable 

 to the law which is concerned in grouping together the bubbles and liquid 

 vesicles. 



But in the cases we have heretofore been considering, the disks, bubbles, 

 and other factitious objects are not in precisely the same conditions 

 as the blood-corpuscles — the former being only partially, or not at all 

 submerged in liquid, while the latter are entirely so, and nevertheless they 

 run together into rouleaux and groups. It may fairly be asked if the 

 artificial bodies will do the same. The answer obtained by experiment is, 

 that the moment these disks or bubbles are entirely submerged, they lose 

 at once their attraction for each other and fall apart. 



For several years I unceasingly asked myself the cause of this difference 

 in behaviour. I at length found that when small bodies, such as disks of cork 

 or gelatine, are first wetted with water, and then submerged in a liquid with 



