142 PHARMACEUTICAL BACTERIOLOGY 



from the living support and in so far it constitutes a symbiotic relationship. 

 The morphological adaptations favoring climbing are however primarily 

 for the purpose of bringing the assimilative tissues nearer the sunlight, 

 and away from excessive moisture. The support is necessary in order 

 to enable them to enter into successful competition with other plants. 

 In many instances the supporting plant plays the part of a host as in 

 true parasitism (Cuscuta). There is little doubt that the members of 

 the Dodder family were originally climbing plants which took almost 

 their entire nourishment from the soil and air. The contact with the 

 supporting plants gradually developed a wholly parasitic habit. In 

 many of the climbing plants the supporting function predominates while 

 the symbiotic relationship remains practically zero. This is especially 

 true of the large thick-stemmed climbers of the tropics. 



Highly interesting though little understood, are the frequently occur- 

 ring neoformations in animals, such as tumors (epithelioma, limpoma, 

 osteoma, sarcoma, carcinoma, etc.) and cysts of various kinds. It is 

 supposed that these growths are neoformations arising from the develop- 

 ment of dormant embryonic cells. These pathologic growths are special 

 body cell proliferations, as has already been stated. Why certain tissues 

 should suddenly take on this highly antagonistic attitude toward the 

 rest of the body cells (somatic cells) is not known. It is a fact that these 

 circumscribed degenerative cell proliferations present all of the charac- 

 teristics of a foreign attacking parasite, sapping the vitality and even 

 destroying the life of the host. Much attention has been given to cancer 

 research within recent years but no conclusions have as yet been reached, 

 neither as to cause or as to cure. 



In conclusion we shall cite a few symbioid phenomena from the insect 

 world and show how they are gradually converted into undoubted sym- 

 bioses. Different species of wasps narcotize or paralyze spiders, crickets 

 and caterpillars, by stinging, thus rendering them motionless. How the 

 wasp learned to perform this remarkably delicate operation, through which 

 the animal operated upon is paralyzed and rendered entirely helpless 

 without destroying life, is not known. Not even the most skilled surgeon 

 now living can perform an operation of this kind with the precision and 

 the nicety with which the apparently awkward and plundering wasp per- 

 forms it. In this condition the narcotized insects are sealed into the 

 wasp's nest containing the eggs, in order to serve as food for the young 

 wasp. This condition becomes more complicated by the intrusion of 

 another wasp which unobserved lays its egg in the nest already supplied 

 with the necessary food. The foreign egg develops first and the young 

 wasp not only eats the food supplied by its foster mother, but also the 

 eggs. From these conditions to true parasitism is only a step. Some 



