CONTROL Oi- ANIMAL J'AKASITES ^oO 



noninnuiiiH' man witli the same virus. The man took sjiialljiox as usual ; 

 Jami'S did not. Crude methods at first, imikiut,^ iuevitaldc mixcil inocu- 

 lations with other germs, raised vioh'ut ohjeetion to va<-cination, hut 

 at that timt' the disease itself was so much mnic sriious than any such 

 coni[)lications, that the ]»ractice spn ail raiiidly over the worM. MimIith 

 bacteriological metho<ls luive ma<it' Um- \iriis safe, so that countries 

 like Germanv, in which vaccination under two years, with revaccination 

 Itetweeii tell and twelve, is Compulsory, have rednced snuillpox to the 

 vanishing point. In Kngland, however, the old oi>i)ositi<»n has persisted, 

 ami this has resulted in many serious local epidemics. Tin' same is 

 true of our own country ami Canada. A new ditliculty has also ari.sen. 

 The di.sea.se has heen so nearly exterminated that even the most con- 

 scientious people are saying: " ^^'hy vaccinate our children against a 

 disease to which they will never be expo.sed?" This argument is suf- 

 ficiently answered by the nniny local ej)id<'mics of recent years. Study 

 carefully the history of at least one such eiademic.^ 



No less than eighteen other cities and towns in New York State, ami 

 several more in other states, were infected with smalli)ox from Niagara 

 Falls in 1014, and Canada was ()l)liged to (puirantine against the city. 

 Is it right for one person, or one city, to endanger the safety of others 

 in this way? Look up the prevalence and mortality of smallpox, and 

 methods of "inoculating" from mild cases, before l-SOO, and compare 

 with present conditions. Study also the story of the introduction of 

 smalli»ox into America by the Spaniards. Tt is said to have killed 

 ;;..")()( ),()()() natives in ^lexico. 



The trypanosomes (trypanon, "auger"; soma, "body"). This genus 

 contains al>out sixty known .species, which live as free-swimnjing juira- 

 .sites in the blood plasma of many vertebrates, from fishes to num. Their 

 primary ho.sts are probably bloodsucking Hies, which, at any rate, act a.s 

 carriers. Surra, a disea.se of cattle, horses, and cannds in India and the 

 Philippines, is caused by T. rransli; and nagana, ov tsetse-fly disease, 

 whi(di long made impossible the introduction of Kuro])ean cattle, horse.s, 

 and sheep into Last Africa, is caused by a similar bl.x.d jiarasite, 

 7'. hnicri. Xearer home a serious di.sease of horse.s, dourine, long known 

 in Europe, and more recently reported from western Canada, is caused 

 by 7'. etiuipfinhtm. This forms a notable exception among diseases of 

 this class in being spicad exclusively by breeding, and has no known 

 connection with biting insects. 



1 1)1. ].. M. William.s, "Smallpox Kpideiuic at Nia-ara Falls,"* Amrriran 

 Jnunud <>t Pahlir Ihnlth. Vol. V (I'.nr,). p. 4l':b 



