292 



'JCIENCE. 



[N. S. Vol. XXII. No. 558. 



eggs may vary very greatly owing to dif- 

 ferences in temperature. Immediately after 

 the larva is born it crawls to the summit 

 of a blade of grass or grass stem, and there 

 awaits the passage of some animal. If an 

 ox passes by and grazes on the grass, the 

 tick at once crawls on to the animal, and, 

 having secured a favorable position, starts 

 to suck the ox's blood. It remains on the 

 ox for some three or more days, when, hav- 

 ing filled itself with blood, it drops 'off and 

 lies among the grass. The first moult, 

 under favorable conditions, takes twenty- 

 one days, when the nympha emerges. In 

 the same way the nympha crawls on to an 

 animal and fills itself with blood. As a 

 nympha it also remains on the animal for 

 about three or four days. It again drops 

 off into the grass, and at the end of eighteen 

 days emerges from its second moult as the 

 perfect adult male or female. The males 

 and females again crawl on to an ox, where 

 they mate. After this the female tick in- 

 gests a large quantity of blood, which is 

 meant for the nourishment of the eggs, and 

 again drops off, sometimes as early as the 

 fourth day, into the surrounding grass. 

 After about six days she lays her eggs in 

 the ground, and the cycle begins again. 



These ticks are very hardy, and in the 

 intermediate stages can resist starvation 

 for loUg periods, so that a larva or nympha 

 or adult tick may remain perched at the 

 end of a blade of grass for some months 

 without finding an opportunity of trans- 

 ferring itself to a suitable animal. On this 

 account it comes about that even if all in- 

 fected cattle are removed from a field the 

 ticks in that field will remain capable of 

 transferring the infection to any healthy 

 cattle which may be allowed into this field 

 for a period of about a year. At the end 

 of a year or fifteen months, however, the 

 infective ticks are all dead, and clean cattle 

 may be allowed into the field without any 



risk. If one takes these facts into consid- 

 eration it will be seen that a single ox may 

 spread this disease for a distance of some 

 200 miles, if trekking through the country 

 at the average rate of ten miles a day. For 

 example, an ox is infected by a tick; for 

 fourteen days the animal remains appar- 

 ently perfectly well ; it has no signs of dis- 

 ease, nor has it any fever. It is capable 

 of doing its ten miles' trek a day. At the 

 end of fourteen days the temperature be- 

 gins to rise, and the animal begins to sicken 

 with the disease, but for the next six days 

 the ox is, as a rule, able to do its ordinary 

 day 's march. During most of this time the 

 brown ticks have been crawling on to this 

 ox, becoming infected, and dropping off 

 every three or four days. It can readily, 

 therefore, be seen how much mischief a 

 single infected animal can do to a country 

 between the time of its being infected by 

 the tick and its death some twenty-four 

 days later. As a matter of experience, 

 however, the disease has never been found 

 to make a jump in this way of more than 

 fifty or sixty miles, as, of course, it is very 

 rare that a transport carrier will take his 

 oxen more than that distance during the 

 twenty days. 



At the present time it may be said that 

 there are about 500 infected farms in the 

 Transvaal. During last year some 15,000 

 cattle died of the disease, and in the 

 affected districts it may be said that there 

 are still some 30,000 cattle alive. When 

 one considers the value of the cattle dead 

 of this disease, which may be said to be 

 about £200,000, it is evident that money 

 spent on the scientific investigation of the 

 causes and prevention of stock diseases is 

 money well spent. I am informed that all 

 the South African governments are cutting 

 down their estimates this year, and are in- 

 clined to reduce their veterinary staffs and 

 the amounts devoted to research regarding 



