442 



THE AGUIGVLTVTttAl JOUBNAL. 



They would not actually say that they 

 thought theie was no chance, but let it be 

 inferred that there appeared so little 

 chance that it were much better to ex- 

 pend one's energies in developing and 

 encouraging artificial remedies, the use of 

 which they considered would probably 

 stilt be profital)le, if not absolutely 

 necessary, in the evest of the best possible 

 parasites they could imagine being fouml. 

 On the other hand the Californians were 

 quite hopeful in their views." 



Plant and Fruit Imports. 



Finds of injurious insects among plants 

 imported from abroad are reported as 

 rather numerous. ' Two large consign- 

 ments of assorted fruit trees from Sydney, 

 New South Wales, together valued at 

 £.'00, were found to bring with them the 

 San Jose or Pernicious Scale and the 

 Black Peach Aphis. Both lots were confis- 

 cated, and every tree and all cases and pack- 

 ing material burned on the beach. The San 

 Jose Scale is the notorious insect which 

 has made such a commotion among horti- 

 culturists in the United States of recent 

 years, and has led to Canada and several 

 European countries legislaHng against 

 Americaii nursery stock. Later in the 

 Tear several ash trees were found badly 

 infested with the Oyster Shell Bark-louse. 

 These trees were promptly burned." 

 These finds, with othei-s, go far to confirm 

 the necessity of the regulations recently 

 brought into force in Natal as neither the 

 San Jose or the Oyster Shell Bark-loose 

 of the apple are known to occur in this 

 Colony. 



Tick — Hbartwatbr Investigations. 



Particularly interesting in the report 

 are the experiments designed to establish 

 the connection ])etween tick parasites and 

 the heartvvatcr disease of sheep. These 

 are given in detail in the report, and the 

 following summary by the author will be 

 read with general interest :—" Research 

 in the i)articular line was suggesle<l by 

 the findings of Government Veterinarian 

 Dixon in regard to the contraction of the 

 disease on the veld inde])endent of food 

 and drink (see A()ric'uiiur:(l Jourval, 

 June 2;5rd, 1898 >, by the popular notion 

 amongst farmers that the Bont Tick was 

 concerned (for instance, see evidence of 

 Mr. J. Weljb before Cattle Diseases Com- 



mission, 1876), and by sundry facts that 

 came under the writer's observation 

 whilst elucidating the life history of the 

 Bont Tick at Fort Beaufort in 1899. 

 Indications that the Bont Tick was con- 

 cerned were determined by a minox ex- 

 periment reported a year ago. Now it is 

 a pleasure to record thai a carefully con- 

 ducted experiment, carried out in the 

 first half of the past year, has demon- 

 strated conclusively that the species of 

 tick in question {Amhlyomma habrceum, 

 Koch\ is an agent in the transmission of 

 the disease. More recent M^orks show 

 what would rationally be expected, that 

 the attack of the tick is normally non- 

 infective. A few only are needed to give 

 the disease when these come from a 

 diseased animal, and this is true even 

 when the interval between the ticks 

 leaving the diseased animal and gaining 

 access to the susceptible one is of six or 

 eight months' duration. When the dis- 

 ease liecomes manifest, the ticks that 

 conveyed it may have already left, which 

 fact explains how it is that no ticks what- 

 ever are to l)e found in some affected 

 animals. Other officers of the Govern- 

 ment have found that the disease may be 

 communicated by blood inoculation ; but 

 to ensure death virulent blood to the 

 amount of three or more cubic centi- 

 meters is used— an amount scores of times 

 in excess of what is drawn by the number 

 of ticks necessary to cairy the infection 

 simplT identical to their bite. In a recent 

 experiment five nymphal ticks (Bont) 

 produced a fatal case. The ticks must 

 infect through the skin, whilst blood in- 

 oculation, to be uniformly successful, 

 must be intravenous ; even ten to fifteen 

 cnljic centimeters of virulent blood in- 

 jected subcutaneously, Mr. Dixon has 

 stated to the writer, is not certain to pro- 

 duce the disease in over three-fourths ot 

 the animals inoculated. Such facts as 

 these appear to indicate that the disease is 

 due to a micro-organism in the blood 

 which is taken up by ticks in their feed- 

 ing, and in the Bont l ick at least then 

 undergoes development in which it be- 

 comes immensely intensified in virulence; 

 in other words, it appears that the tick is 

 an intermediary host for the disease 

 organism not yet discovered that causes 

 the malady. It has not yet been shown 

 that other species of ticks may not convey 



