814 



Parasitism as cause of (jiunmosis. 

 The connection between loounding and parasitimi. 



Wounds ill peach bmnclies trealed with poisoiioiis substances, 

 such as sublimate, produce gum much longer and more copiously 

 than the like wounds without sublimate. Other poisons have quite 

 the same effect. Now it is clear that the direct intluence of para- 

 sitism on the organism must be sought in the action of some 

 poisonous substance. Hence it seems certain that what these three 

 causes have in common, namely necrobiose, or the slowly dying of 

 the cells surrounding the dead ones, is the base of gummosis, and 

 that parasitism, where neci'obiose lasts as it were endlessly, must 

 be the most powerful instigator of the process. 



That this simple view of the question has not yet taken root in 

 science is proved by the most recent treatise on our subject by 

 MiKOscH, ^) illustrated with beautiful anatomical figures. After the 

 publication of Dr. A. Rant and myself of 1905, he described the 

 relation of mechanical wounding to gummosis. But he did not think 

 of poisoning experiments, nor has he any belief in the intluence of 

 parasitism on gum formation. Wiesner, in his recentl)- published 

 paper on gums in the new edition of his "Rolistoffe des Ptlanzen 

 reichs", is also of the same opinion as Mikosch. 



For my object a short discussion of a few examples of parasitism 

 will suffice. 



The little caterpillar Grapholitha weberiana makes borings into the 

 bark of plum and apricot, and if the outermost corklayer is removed 

 by shaving it off, the butterfly finds so many fit places for deposing 

 its eggs, that the larvae creep in by hundreds and make new borings 

 from which later the gum flow^s out. These holes are coated with 

 a layer : of slowiy dying cells, whence the stimulus extends, which 

 produces thé gum canals in the contiguous "cambium". By cambium 

 I simph' understand the not yet differentiated division products, 

 "young wood" and young phloeoterma. The necrobiotic cells, clothing 

 the continually extending holes in the bark, and the great numbers 

 of new individuals of the caterpillars, make the gum production a 

 chronical process. 



To explain the formation of the enormous quantities of gum 

 produced in this way, it seems only necessary to think of mechanical 

 wounding and not of emy special excretion from the animal. But it 

 must be noted that the space, where the caterpillar lives during its 



1) Untersuchungen über die Entstehung des Kirschgummi. Sitzungsber. d. Kais. 

 Akad. d. Wiss. in Wien. Mathem. naturw. Klasse. Bd. 115, Abt 1. Pag. 912, 1906, 



