1912.] Summary of Agricultural Experiments. 1041 



Bracken Poisoning. — In connection with so-called bracken poison- 

 ing, to which reference was made in the report for 1909, experimental 

 feeding on bracken again failed to produce the characteristic symptoms 

 of the disease. In one case the owner of affected cattle attributed 

 the illness to Tormentil (Potentilla tormentilla, Linn.), and a heifer 

 fed at the laboratory on this weed, taken from the pasture where 

 illness was prevalent, became affected, and, on examination, showed 

 all the appearances associated with the mysterious " bracken poison- 

 ing." It is pointed out, however, that there is a distinct possibility of 

 the tormentil — which is a common weed in most parts of the country, 

 and usually regarded as harmless — having merely acted as the carrier 

 of some form of contagion from the pasture on which sick animals 

 were grazing. 



Origin of Thoracic Tuberculosis in Calves (Journal of Comparative 

 Pathology and Therapeutics, September, 19 11). — In this article, taken 

 from the Annates de VInstitut Pasteur, Vol. xxv., No. 7, M. P. Chausse 

 describes some of the recent work carried out to compare inhalation 

 and ingestion as means of infection in tuberculosis, and gives an 

 account of experiments carried out by himself in this connection. Both 

 lambs and calves were submitted to infection in the two ways. It was 

 found that when virulent material, taken from diseased animals, was 

 (after being diluted very considerably) sprayed into the air of the houses 

 where animals were kept, tuberculosis of the lungs was contracted in 

 (every case. The disease was not so easily produced by feeding 

 animals with the infective material, and from this, taken along with 

 the results of his examination of the carcasses of a large number of 

 young calves, the writer argues that in about 90 per cent, of cases 

 tuberculosis in calves is caused by inhalation, and in only very few 

 is infection produced through the food. 



From this, the conclusion is drawn that in children the risk of 

 infection through consuming cows' milk is slight compared with the 

 chances of infection through being placed in intimate contact with 

 tuberculous people, especially in insanitary surroundings. 



Horticulture. 



The Effect of Grass on Trees (Thirteenth Report of the Woburn 

 Experimental Fruit Farm, 191 1). — In their Third Report, the Duke of 

 Bedford and Mr. Spencer U. Pickering drew attention to the extent 

 of the damage done to young fruit trees by grass. In the report under 

 notice an account is given of experimental work that has been carried 

 out since then, to test further the effect of the grass and to try to obtain 

 a satisfactory explanation of its action. 



It has been found that the extent of the effect depends on certain 

 conditions, such as character of soil, age and kind of tree, and the 

 rate at which grass spreads over the ' area cleared when the tree is 

 planted, but in all the experiments extending over sixteen years, and 

 carried out at several centres, there was only one case in which the 

 deleterious action of the grass was not marked. In the majority of 

 cases it was considerable, and in many it caused the death of the 

 tree. In none of the experiments has any recovery from the effect 

 been noticed, except in cases where the roots have extended beyond 

 the grassed area into cultivated ground. Ten years' records of the 



