Nov. 23. 1918 Observations and Experiments on Intestinal TrichincB 479 



intestina ' forms is a further confirmation of the view that the tissues of 

 the organism are not passive but take an active part in the reaction. The 

 increased susceptibihty of the intestinal worms to potassium cyanid is 

 also probably independent of the cuticle since this increased suscepti- 

 bility expresses itself in many other ways which are more or less independ- 

 ent of permeability of the membranes of the worms to substances in solu- 

 tion. The loss of tolerance of the intestinal worms to cold, their failure 

 to survive outside of the host for any length of time, their sudden disin- 

 tegration in salt solution, and the gradual reappearance, though to a 

 markedly lesser degree, of their tolerance to various conditions would 

 indicate that the differences in susceptibility between the intact larvae 

 and the rapidly developing forms are due to a complete reorganization of 

 the latter as a result of the resumption of differentiation and development. 

 The encysted larvae are quite inactive under normal conditions. They 

 neither increase nor decrease in size, but maintain a morphological balance 

 which must have its basis in a delicate adjustment between their nutri- 

 tive income and their outgo as a result of their processes of oxidation and 

 excretion. With the resumption of growth and further differentiation in 

 the small intestine, the physiological adjustment between income and outgo 

 rapidly breaks down, their constructive metabolism running far ahead of 

 the destructive processes. This leads to an increase in size of the animal 

 and to a differentiation of organs not developed in the encysted larvae. 

 The intestinal forms in the early stages are thus characterized by a 

 period of rapid growth and may, therefore, be regarded as physiologically 

 younger than the encysted forms. Under the intestinal influences they 

 experience a rejuvenescence, exhibiting a high metabolism which decreases 

 again with age. Parallel with their aging they become more tolerant to 

 adverse conditions. In other words, in the intestine the lar\^ae recom- 

 mence a typical life cycle, marked at first by a period of rapid growth and 

 an extreme sensitiveness to unfavorable external conditions, and followed 

 by a period of relative stability and gradually by a reduction in sus- 

 ceptibility to adverse influences. 



ATTEMPTS TO INDUCE MOLTING IN THE LARV^ ARTIFICALLY FREED 

 FROM THEIR CAPSULES 



Trichinella spiralis is particularly remarkable in its lack of host speci- 

 ficity. It is capable of reaching maturity in almost any mammalian 

 host and is even able to develop in the intestine of birds. This adapta- 

 bility to a varied environment would indicate that the factors favorable 

 for its development are the general conditions prevailing in the intestine 

 of warm-blooded vertebrates, such as temperature, food, alkalinit}-, etc. 

 It therefore appeared to the waiter that it would not be a hopeless task to 

 attempt to induce the larv'se isolated from their cysts to molt on artificial 

 media. Thus far all efforts have proved futile, but the work is being 



