191 1] William J. Gies 3^3 



The local edemas following the bites or stings of insects have a 

 special interest. In quite a number of these the sting carries f ormic or 

 other acids into the tissues. Here we have a direct etiological factor for 

 the production of the local edema. In others, poisons are injected 

 which have a well-marked reducing power, By this means a local group 

 of cells are placed in a State of lack of oxygen through chemical means. 

 It is worthy of note that to start with and during the period of greatest 

 swelling such insect stings are white, and not until later do they become 

 red. The increased blood flow so necessary in most explanations of 

 these local edemas does not occur until the edema has begun to subside. 

 Instead of the blood circulation determining the edema, the edema 

 determines whether the circulation shall continue through the affected 

 part or not. (Page io8.) 



This explanation of the nature and cause of local edemas can be 

 further tested. The cdematous wheals following bites or stings can be 

 mimicked perfectly with a gelatin plate and a little acid. If with a 

 fine hypodermic needle a little formic acid is stabbed into such a gela- 

 tin plate, and the whole is then laid into water, an urticarial-like wheal 

 develops about each spot pricked with the needle, which in shape and in 

 the rate of its development is not unlike those which follow the bite of 

 an insect or the introduction of the formic acid laden needle into the 

 skin. (Page io8.) 



In Fig. 44 are shown some wheals which developed accidentally on 

 the surface of some of my gelatin discs. The particular disc pictured 

 had lain for thirteen days in a n/20 hydrochloric acid Solution. The 

 hyaline gelatin does not photograph easily, and so the figure does not 

 indicate how clearly these wheals imitate such as are observed clinically. 

 Those shown here are due to local infections of the gelatin with a 

 mold. In place of the perfectly smooth surfaces such as these gela- 

 tin discs ordinarily show, we see them here studded with small mounds 

 indicative of irregularities in the absorption of water. The cause for 

 these local swellings may be a twofold one. As the mold developed 

 while these discs were lying in dilute acid Solutions, I question whether 

 an additional local production of acid (of which the molds are capable) 

 gave rise to the local swellings. The affected spots were softer than the 

 surrounding gelatin, and later became almost liquid. I think, in conse- 

 quence, that the gelatin suffered a partial digestion under the influence 

 of proteolytic ferments manufactured by the mold in the affected 

 spots. Such a partially digested gelatin corresponds with the Beta- 

 gelatin of Traube, and this we know from Wolfgang Ostwald's^" ex- 



**" Ostwald : Archiv für die gesammte Physiologie, 1905, cix, p. 277. 



