302 



SCIENCE 



[N. S. Vol. XL VII. No. 1213 



THE VALUE OF ZOOLOGY TO 

 HUMANITY 



The task assigned me is to present to you 

 as adequately as may be possible in the brief 

 time allotted this topic, the significance of 

 studies on animal parasites for the progress 

 of the human race. 



Since the earliest times of unwritten his- 

 tory human records bear evidence to the 

 bitter warfare waged by men of all races 

 against the large carnivores that threatened 

 their existence and played havoc with the 

 useful animals they had brought under con- 

 trol. As time went on and his purview 

 gained in breadth man turned his attention 

 to noxious types such as the snakes, and to 

 smaller forms like the rats that are real 

 though less conspicuous foes. And, finally, 

 in very recent years, he has learned to 

 understand that minute organisms like the 

 bloodsucking insects are not only sources of 

 discomfort but also play an essential part 

 in the transmission of many of the micro- 

 scopic organisms that produce disease. He 

 knows that these organisms both plague 

 and destroy the domesticated animals, that 

 they greatly reduce his own efficiency and, 

 threatening his very existence, drive him 

 away from rich and fertile territory or in a 

 single epidemic wipe out families, villages, 

 or even whole nations. In short, animals 

 nowhere affect man more extensively and 

 more seriously than in those relations in 

 which they appear as the agents in produc- 

 ing or transmitting disease, and it is of 

 fundamental importance for the progress, 

 prosperity and even existence of the human 

 race that those relations should be investi- 

 gated, determined with precision, and 

 brought under control. 



This in a broad general way is the prob- 

 lem of parasitology, and it is important at 

 the very outset to indicate that it is not set 

 off from other studies on animal life by any 

 hard and fast limits. The structure of 



parasitic animals can be interpreted rightly 

 only by the results of knowledge gained 

 concerning the anatomy of free-living 

 forms ; the development of parasitic species 

 depends for its explanation on the results of 

 studies on the development of animals gen- 

 erally; the habits of parasite and host are 

 so intimately interlocked that the key to the 

 life history of a parasite is found in the 

 associations of the host. Now the recogni- 

 tion of this intimate and necessary connec- 

 tion between zoology in the narrower sense 

 and parasitology is of relatively recent date 

 and has favored promptly and conspicu- 

 ously the contributions of zoology to hu- 

 man welfare. Brief reference to the history 

 of science may serve to make this point 

 somewhat clearer than it appears in the 

 general statement. 



As a matter of fact parasitology is of 

 ;the oldest phases of the study of animal 

 life and its even jet faintly recognized re- 

 lations to man. Diseases caused by animal 

 parasites played evidently an important 

 part in the economy of the nations of antiq- 

 uity. The oldest medical works that have 

 come down to us give intelligible records of 

 the presence in man of such guests and in 

 some oases recognizable descriptions of the 

 parasites themselves. This study pursued 

 under the direction of the priests and med- 

 ical men was developed apart from other 

 fields of zoology. As a result the knowledge 

 thus gained reached more consideraible pro- 

 portions and was more widely disseminated 

 •at an early date than the general knowledge 

 of animal structure or of animal function. 

 To some extent the separateness of the two 

 fields exists at the present date, to the dis- 

 ^ advantage of scientific progress and human 

 welfare. 



The parasites known to the ancients were 

 of course the larger, more conspicuous 

 forms. And while some inlportant facts 

 were included, thedr knowledge was con- 



