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SCIENCE 



[N. S. Vol. IAI. No. 1350 



and had planned work to reveal the facts. 

 Fortunately the department of dairy hus- 

 bandry of this institution, under the leader- 

 ship of Professor C. C. Hayden, has had in 

 progress for many years an investigation with 

 dairy cows contributing evidence directly on 

 this subject; and during the past summer the 

 writer has had under observation this same 

 group of cows on which he was conducting 

 mineral feeding experiments. 



Mr. Hayden permits me to make the follow- 

 ing observations on these cows. Since 1911 

 a group of Holstein-Friesian cows has been 

 maintained on dry feeds and silage alone. 

 No green feed has been allowed. Several of 

 the animals now in this group were born in 

 the same and have grown to full maturity 

 without having a bite of green feed. Ex- 

 tensive evidence is at hand, therefore, as to 

 the importance of the suggestion of Hart 

 and associates, as bearing on lactation in 

 cattle. 



This group of cows has grown to normal 

 weights, and has produced and reared calves 

 without marked or certain irregularity or 

 abnormality. The milk production has been 

 fair only, it being obvious that with normal 

 treatment these cows would have given more 

 milk. They do not have normally keen ap- 

 petites and some are easily forced ofE feed. 

 They will not eat enough feed to support 

 maximum milk production. They fall away 

 during lactation a little more than is cus- 

 tomary, but pick up again after going dry. 

 These cows have been in noticeably less 

 thrifty condition, as indicated by flesh and 

 coats, than the balance of the herd, which 

 goes to pasture, and it has been apparent that 

 they crave something which they do not find 

 in the ration. 



During the past summer the writer has con- 

 ducted palatability tests on these cows, with 

 various mineral supplements. They have 

 manifested a keen desire for mineral feeds, 

 having eaten, in several short periods, from 

 approximately three fourths of a pound to 

 more than one and a fourth pounds of mineral 

 supplement per head per day. These supple- 

 ments have consisted of various calcium phos- 



phate and carbonate preparations, fed alone 

 or mixed with common salt. It has been 

 shown that the desire of the cows for these 

 feeds has not been wholly or predominantly 

 due to the liking for salt. The avidity with 

 which these cows eat steamed bone, considered 

 in connection with our finding that negative 

 calcium balances normally prevail during 

 lactation in cows on dry feed, and the con- 

 clusion of Hart and associates that fresh grass 

 favorably affects calcium retention, suggests 

 that these dry-fed cows are in a state of min- 

 eral depletion, especially while giving milk. 



It appears, therefore, that the suggestion of 

 Hart and associates is a matter of practical 

 importance as relating to milk production, 

 but that rations of dry feeds and silage, 

 though probably deficient in some constituent, 

 are not entirely lacking in any essential. 



The most important work indicating the 

 dependence of calcium metabolism, especially 

 of the teeth, upon vitamines, which has come 

 to the writer's attention is an extensive and 

 unusually successful investigation with guinea 

 pigs (as yet unpulblished) by Dr. Percy R. 

 Howe, of Harvard University. 



E. B. Forbes 



Depaktment op Nutrition, 

 Ohio Agricultukal Experiment Station 



swarming of anopheles 

 To THE Editor of Science : It may seem a 

 little late to publish this note, but, on account 

 of a long absence from the country, I have 

 only just seen reference, in the Review of 

 Applied Entomology for May, 1920, to Mr. 

 C. S. Banks's article entitled " The Swarm- 

 ing of Anopheline Mosquitoes" published .in 

 the Philippine Journal of Science for Sep- 

 tember, 1919. Mr. Banks is quoted as stating 

 in the article that, although the swarming of 

 mosquitoes has been constantly reported, "no 

 mention seems previously to have been made 

 of this habit in the case of Anophelines." As 

 a matter of fact the late Mr. Frederick Knab 

 published in Psyche for February, 1907, a 

 rather extended note on the swarming of 

 Anopheles maculipennis Say. This note is 

 reprinted in full in the Monograph of the 



