294 JAMES CRAWFORD WATT. 



namely, that the so-called spherules are in reality flattened discs. 

 During their vibratory movement many of them have been ob- 

 served to slowly roll over and a narrow, thin edge is presented to 

 the view instead of the circular outline. The appearance reminds 

 one very strongly of a red blood corpuscle. 



The largest and clearest spherules (Figs. 19-22) were formed 

 in gelatin whose pH was between 4.7 and 7.5 — that is, all in gelatin 

 on the alkaline side of the isoelectric point — but in specimens whose 

 reaction was either weakly acid or weakly alkaline, the neutral 

 point being 7.0. This is the zone in which is obtained the forma- 

 tion of the largest spherules. Untreated gelatin, used for all the 

 previous series of reactions without regard to hydrogen-ion con- 

 centration, has a pH 6.0 and so is within this zone. The pH of 

 human blood and many tissues also lies in the alkaline part of this 

 zone. 



It is interesting to note that in strong acid members of the series 

 precipitation is rapid, and while spherules may early be present, 

 the deposit in the course of a short time becomes entirely crystalline 

 in structure. In strongly alkaline members precipitation is very 

 complete, but the deposit remains for an indefinitely long time in 

 the form of small, discrete spherules, which do not grow or fuse, 

 and which continue to exhibit Brownian movement. No crystals 

 appear in these latter cases, even after the lapse of many months. 



In the intermediate zone of weak acid, neutral, or weak alkaline 

 gelatin both spherules and crystals appear in quantity, and the 

 spherules are very large. In the part of this zone in which the 

 hydrogen-ion concentration of blood and many tissues lies the 

 deposit is mostly in the form of small spherules and the tendency 

 to crystallization is very poor. This is essentially a colloidal phe- 

 nomenon and seems significant in view of the fact that it has fre- 

 quently been found that certain drugs in colloidal form have a 

 much better therapeutic effect, have a much less damaging effect 

 on healthy tissues, and are much more pleasant in their administra- 

 tion to the patient. As an example of this, compare the actions 

 of silver nitrate and of argyrol, a colloidal silver vitellin. The 

 colloidal preparation much more nearly approaches the condition of 

 the tissues themselves and the reactions ought to be of a more col- 



