382 



milk is proliiildy explained, laif^ely at least, l>y the laws of liquids. The film of 

 <;is(iii aromiil tlie fat Las a sniface ttiision difterent from that of the fat, aud this 

 tt'M>i()ii must lie overcome in order that the fat globules may fuse togetlier. Any- 

 thing; wliieli would tend to rujiture tliat !ilm would assist in the fusion an<l aid tlie 

 solution of the glolmles, and hence the addition of acids or a shaking will tend to 

 make the fat globules fuse together. Lastly, it would seem that a change takes 

 jdaee in the milk shortly after being drawn. It becomes less liquid, and a .slimy 

 sulfstauce is forme<l, which tauses the globules to unite together into groups. This 

 substance may be fibrin, and is at all events of a protcid nature. In all cream of 

 (our.se this material will be present, aud its presence is an important factor in the 

 consideratiiui of the tn;itment of cream in butter making. 



Til oautluu's studies liave beeu iniuk' on ii|uMie(l t ream tVoiii twodUVt-r 

 ent crcaiiieries and fi()ni the Storrs Sebool dairy. and on cream ripened in 

 tlie laliniatory at dilVerent sea.-^ons of tlie year. His method of work is 

 dcsri ilicd in detail. He considers the estimation of the actual nund>er 

 olhnctciia ill cuaiii as of very litth- value, since the nund)er is so larjje 

 (liciim estimated at LMM».(t(M>-L».(l(M>.(»(M> in a sinf,de droj) the size (»f apin 

 head ill some of the sju'ciim-ns studied) that anytiiiiij,' like an aitjiroxi- 

 matioii to iicciiiacy is impossihle. 



I liave found a larger numlxr of baeteria in centrifugal cream than in the skim 

 milk taken at tin- same tinn\ Tin- slime that eullects \tu tlie drum of the macliiue 

 was found to Iiave nuue tJian either tin- milk or the cream. This is the same result as 

 was rearhcd liy Wyss, who stated that this sliun- eimtained seven times as nmny 

 bacteria as the milk. I did not find so great a numerical ilifterence. 



One of the rhicf oltjecis in this study lias been to determine h<»w great a variety 

 there exists in the bacteria found in normally ripening cream, and to see if there is 

 any one or any few species which .ire distinetly eharacteristic of the process. * * • 

 At least .jOditVerent species or varii'ties of organisms liave lieou isolated and studied, 

 including tiaetcria, yeasts, and molds, .\moug them are many of the well-kuowu 

 Coiiiis descriliid in liacteriological text-lKioks, 1»ut also a large numtter of forms whiih 

 do not agree with any descrii)tion that I have been able to lind. * * * Fnuii this 

 great variety we must conclude that tlie special series of forms of bacteria which are 

 present in any specimen of ri|iening cream is more or less a matter of accident. In 

 the cream tlieriis a great battle of the forms with cacli other. The victors will be 

 those which chance to get the Itest start, and this dejieuils upon such a variety of 

 circumstances connected with the collecting of the cream that it is entirely beyond 

 our kuowlcilge. No means at the ccuumand of thf dairyman can regulate the 

 bacteria sujipli*'*! him by his eustoniers nor the variety which produce the rii»eniug 

 of his cream. Uniformity in the ripening jtrocess does not ocmr even under seem- 

 ingly uniform conditions. ' * ' The experiments in collecting the forms «>f 

 bacteria found in ripened cream are still in progress and new varieties are being 

 constantly found. I shall therefore reservi' a s)»ecial description of the individual 

 8]>ecies until it seems that a tolerably complete list of the common forms in cream 

 can be given. It may l>c that a complete list can never be given, and that the forms 

 are constantly uinlergoing modilicaticui. To determine this will of course require 

 a hmg scries of years. .\t the present time, at all events, the tuily statements of 

 value wliich can be mad<' are concerning the clas.ses of physiological .iction sliown 

 by the various forms. 



For ccmvenieiue in d( scrijitioii the author diviiles tlie forms into the 

 three classes recognized by Adauietz,t.c.(l) tlio.se causing the formation 

 of acid in the milk, which precipitates the casein; (2) those curdling the 

 milk without rendtiiiii; it acid: and .■») those having no visilile etVect on 



