Jandaby 7, 1916] 



SCIENCE 



33 



sary to study the rates of decomposition in 

 equal and varying concentrations of actual 

 nitrogen. It seems also that if practical con- 

 clusions are to be drawn, it is necessary to 

 approximate field conditions, as nearly as pos- 

 sible, in laboratory tests. This point, it seems 

 to the writer, has not been sufficiently recog- 

 nized in many soil bacteriological studies. 

 The conditions ensuing when relatively large 

 amounts of nitrogenous substances such as 

 dried blood, tankage, etc., undergo decomposi- 

 tion, may conceivably become extremely ab- 

 normal and greatly dissimilar to those ensuing 

 imder field practise. The products arising 

 from the decomposition of 1 per cent, dried 

 blood, under some conditions of bacterial activ- 

 ity may exert, either directly or indirectly, im- 

 portant influences on the further action of the 

 micro-organisms present. Such, for example, 

 is known to be the case in the bacterial decom- 

 position of milk. In fact the course and ex- 

 tent of many chemical and biochemical re- 

 actions is known to be greatly modified by the 

 products of the action. 



As stated above, dried blood undergoes vig- 

 orous ammonification in the several plats 

 studied. It has been suggested that the con- 

 ditions produced by the high concentrations of 

 ammonia or ammonium carbonate, formed 

 from the larger amounts of dried blood and 

 bone meal, may have been unfavorable to the 

 activity of the nitrifiers. With the hope of 

 securing light on this point, preliminary 

 studies have been made by adding varying 

 amounts of ammonium hydrate and ammonium 

 carbonate in addition to 0.25 per cent, dried 

 blood, using a soil in which no nitrification of 

 1 per cent, dried blood takes place. The re- 

 sults showed that in every case the addition of 

 either ammonium hydrate or ammonimn car- 

 bonate partially inhibited nitrification even 

 in the low concentration of 5 mg. per 100 gm. 

 soil. Whether the ammonia was actually toxic 

 to the nitrifying organisms, or reacted un- 

 favorably through physical effects produced or 

 otherwise, can not be definitely stated at the 

 present time. 



Evidence has been obtained that there is 

 considerable seasonal variation in regard to 



the inhibiting effect of 1 per cent, dried blood. 

 With samples drawn from one plat in April 

 and Jime, respectively, 1 per cent, dried blood 

 underwent active nitrification, while no nitri- 

 fication took place in samples taken August 14. 

 In each case 0.5 per cent, and less were actively 

 nitrified. Whatever may be the cause of this 

 phenomenon, the fact still remains to be ex- 

 plained that 1 per cent, dried blood brought 

 about toxic conditions in certain plats, but not 

 pronouncedly so in others. 



W. P. Kellet 

 Univeksity op California, 

 Citrus Experiment Station 



SOME EXPERIMENTS WITH AGENTS CALCU- 

 LATED TO KILL THE TROMBIDIUM 

 HOLOSERICEUM 



The Tromhidium holosericeum or common 

 chicken mite is present in most hen houses 

 throughout the country. It is very trouble- 

 some in the hotter months, especially July and 

 August, when it finds climatic conditionls 

 favorable for its more rapid multiplication. 

 The mites hide in clusters, in the cracks and 

 crevices of the roost pole and in the crack 

 where the roost pole rests on its support. 

 Here they lay their eggs and the young and old 

 emerge to attack the chickens at night. 



The mite finds its way to the hen at night 

 and with its conical piercing apparatus attacks 

 the skin and draws blood. After its feast it 

 leaves the hen and returns to its hiding place. 



In searching the literature at hand in the 

 library of the office of poultry investigations 

 and pathology of this station no trace coiild 

 be found where scientific tests and records had 

 been made to determine just what effect the 

 various parasiticides have upon mites. 



There is common belief that tobacco clip- 

 pings, sulphur, paris green, and a host of 

 liquids are great destroyers of these formidable 

 foes of the poultry house, but no one so far 

 as we could find has actually made the testa. 

 It was thought best to try a score of the more 

 common agents used and to run duplicate 

 tests. 



Mode of Tests. — The tests were run either 

 in open tumblers or sauce dishes so as to have 

 an abundance of air present and to have the 



