Aston. — Chemistry of Bush Sickness. 291 



It having been decided to carry on an extensive series of field experi- 

 ments with a view to ascertain whether top-dressing the pasture with various 

 ertilizers would in any way mitigate or prevent development of the sick- 

 ness, the following substances recommended by me were applied as top- 

 dressings to different paddocks on which the animals were subsequently 

 grazed : Basic slag, superphosphate of lime, rock phosphate, ferrous sulphate, 

 caustic lime, carbonate of lime, nitrate of calcium, potassium - sulphate, 

 blood and bone manure, agricultural salt. Both cattle and sheep were used 

 in these experiments. Kock-salt has been given in most cases freely as a 

 lick. On some experiments water has been given to sheep, and on other 

 experiments no water was given. To cattle water was usually given. 



The results of these experiments, which were conducted under 

 veterinary supervision, will be published in due course. One interesting- 

 feature may be mentioned. The sheep which died of "' bush sickness " 

 on these experimental plots provided with a plentiful supply of salt 

 developed abnormally fatty livers, as the analysis shows. The liver 

 was mainly fat and water. This occurred when the sheep were supplied 

 with water, as at Mamaku, and without, as at Te Pu. It will be 

 noted that the time the sheep were enabled to live on the affected 

 pasture was unusually long. 



The writer desires to acknowledge his indebtedness to Dr. Reakes, 

 Director of the Live-stock Department, for affording information and 

 every facility for carrying on the work, and to Dr. Maclaurin, Dominion 

 Anaiyst, for permission to visit frequently the affected district. Messrs. 

 Clayton, Lyons, Reid, and Kerrigan, Veterinary Officers of the Depart- 

 ment, have proved of great help ; Professors Gilruth (Melbourne), 

 Marshall (Dundee), and Malcolm (Dunedin), have provided many refer- 

 ences and much valuable advice. Mr. R. Alexander, with his practical 

 knowledge in the field, and Messrs. John Chilwell, F.I.C., and Theodore 

 Rigg, M.Sc, in the laboratory have also rendered valuable assistance. 



Experimental. 



In the analysis of animal specimens for copper the method recom- 

 mended by Raoult and Breton (Compt. Rend., 85, 40-42 ; abst. in 

 J.C.S., 32, 1877) was used. The substance (about 100 grams wet or 

 30 grams dry) is heated in a porcelain dish with sulphuric acid untilfthe 

 mass is carbonized. The charred mass is heated to redness in a muffle 

 furnace, and in great part burnt in a good current of air. When the com- 

 bustion becomes difficult in consequence of the fusion of phosphates 

 (chiefly phosphate of iron in the liver specimens) it is exhausted with a 

 small quantity of nitric acid and water. The filtered residue is again 

 incinerated, and the operation repeated until a pure ash is obtained, which 

 is exhausted with more nitric acid. The acid filtrates are evaporated 

 and the nitric acid expelled by evaporating to dryness and taking up with 

 hydrochloric acid. The diluted solution of the ash is now subjected to a 

 current of sulphuretted hydrogen until the copper-sulphide separates out 

 well. This is filtered and incinerated. The ignited residue is redissolved 

 and filtered from any impurity (silica). The solution is made up to a 

 known volume, and an aliquot part taken for colorimetric estimation of 

 the copper by the well-known ferro-cyanide method. The result is always 

 checked by a gravimetric determination made on another aliquot portion. 

 The results agree very closely. I can indorse Raoult and Breton's warning 

 as to the necessity of pushing the incineration till an ash free from carbon 

 remains. Carbon appears to retain the copper with great tenacity. 

 10* 



