28 



NATURE 



[Makch 4, ic,o9 



and neutral salts delay it. It has been found that when 

 aw. class of cell stains on a given agar tilm, other classes 

 do not. By slightly altering the constitution of the agar, 

 I.e. by adding more alkali, acid, or salts, or by trying a 

 different temperature, &c., that class of cell which pre- 

 viously refused to stain will now absorb it. It has also 

 been found that bacteria and other cells are subject to 

 the same conditions, and by this means it has been possible 

 to differentiate them by their rate or coefficient of diffusion. 

 .\ simple method is given for the arrangement of the agar 

 jelly ; and by measuring in units the factors, heat, alkalies, 

 acids, salts, and time, the coefficients of diffusion can be 

 I'xpressed in numerals with the aid of a simple equation, 

 the staining of the nucleus, or the cytoplasm in unnucleated 

 cells, being the moment by which the coefficient is deter- 

 mined. The staining of the nucleus is coincident with 

 death. Conversely, when the coefficient of diffusion of a 

 cell is known, the equation indicates how to arrange an 

 agar film so as to cause staining of the cell in a given 

 time at a given temperature. Examples are given, and 

 among them is one which shows that the rate of diffusion 

 of substances other than stains also appears to' depend 

 on the coefficient of diffusion of the cells. In addition 

 there is a summary, and some suggestions are made as 

 to possible practical applications of the subject considered 

 in the paper. — The origin and destiny of cholesterol in the 

 animal organism, part iii., the absorption of cholesterol in 

 the intestine and its appearance in the blood : C. Doree 

 and J. .\. Gardner. The authors, as a result of experi- 

 ments already communicated to the society and a con- 

 sideration of the work of previous observers, have been 

 led, in the present paper, to formulate the following work- 

 ing hypothesis as to the origin and destiny of cholesterol 

 in the animal organism : — (i) Cholesterol is a constant 

 constituent of all cells, and when these cells are broken 

 down the cholesterol is not excreted as a waste product, 

 but is utilised in the formation of new cells. (2) A func- 

 tion of the liver is to break down dead cells, e.g. blood 

 corpuscles, and to eliminate their cholesterol in the bile. 

 (3) .After the bile has been poured into the intestine in the 

 process of digestion, the cholesterol is re-absorbed, prob- 

 ably in the form of esters, afong with the bile salts, and 

 carried by the blood to the various centres and tissues for 

 re-incorporation into the constitution of new cells. 

 f4) Cholesterol is probably not synthesised in the animal 

 body, and any wastage of cholesterol is replaced by direct 

 absorption from the food. With the view of testing this 

 hypothesis, the experiments detailed in the communication 

 were carried out. On feeding rabbits on food freed from 

 cholesterol or phytosterol, no cholesterol could be found in 

 the fasces. When, however, weighed quantities of chole- 

 sterol were added to this food, a certain proportion wris 

 always absorbed. Analyses of the blood of these animals 

 showed an increase in the cholesterol content in the case 

 of animals fed with cholesterol compared with those with- 

 out cholesterol. Similar experiments carried out on dogs 

 showed that cholesterol was also absorbed from their food. 

 —The origin and destiny of cholesterol in the animal 

 organism, part iv., the cholesterol content of eggs and 

 chicks : G. W. Ellis and J. A. Gardner. This paper con- 

 tains an account of a number of experiments carried out 

 with the view of obtaining evidence of the truth of the 

 hypothesis recently advanced, that cholesterol is strictly 

 conserved in the animal organism, and that it is not 

 svnthcsised by the animal, but taken into its orsrnn'sm as 

 food, at any rate in the growing animal. The (<xt)eriments 

 detailed in this paoer consist of a number of estimations 

 of cholesterol in the total unsaponifiable matter obtained 

 from hens' eggs and newly hatched chicks. The eslimn- 

 t)ons were carried out with the greatest possible accuracy, 

 •and the results leave no doubt that there is no increase 

 in cholesterol durine th" change of the ovu" into the 

 comnlex aggregate of cells constituting the newlv hatched 

 chick. The results sifeem to show a slirhtlv lower per- 

 eentao-e of cholesterol in the chick than in the eesr. but 

 this difference may be due to experimental dififirulties in 

 extracting all the cholesterol from the tissues of the chick. 

 1 he avera.<e percentages of cholesterol in egsrs and chicks 

 .are given in the accompanying t.able. The percentaffes of 

 cholesterol in the chicks are given in terms of the weights 

 of (he original eggs : — 



NO. 2053, VOL. So] 



6 eggs, analysed together ... 

 6 eggs, analysed separately ... 



Average ... 

 6 chicks,, analysed together ... 

 6 chicks, analysed separately 



Average ... 



Difference ... 



Per cent. 



... 0.4896 



... 04121 



... 0.4508 



... 0.4677 



••• 0-3633 



... 0-4155 



■-- 0-0353 



February 18. — Sir .\rchibald Geikie, K.C.B., president, 

 in the chair. — The osmotic pressures of solutions of 

 calcium ferrocyanide, part ii., weak solutions : the Earl of 

 Berkeley, E. G. J. Hartley, and J. Stephenson. 

 This communication records the observed equilibrium 

 osmotic pressures from 25 to 5 atmospheres, and also the 

 electric conductivities of the more dilute solutions ; it is 

 shown that to bring the two sets of observations into 

 accord it is necessary to assume that the salt molecule is 

 associated when in solution. Similar remarks apply to 

 strontium ferrocyanide, and are not inconsistent with the 

 data found for the potassium salt. — The spontaneous 

 crystallisation of monochloracetic acid and its mixtures 

 with naphthalene : Dr. H. ,\. Miers and Miss F. 

 Isaac. In this investigation three different modifications 

 (a, 0, and 7) of monochloracetic acid are described, and 

 the transformations from one modification to another. The 

 behaviour of aqueous solutions of monochloracetic acid 

 was investigated as the solutions cooled by means of 

 observations on their refractive indices. These experiments 

 lead to the establishment of three supersolubility curves 

 separating the metastable and labile regions, corresponding 

 to the three modifications of the acid. These super- 

 solubility curves have also been verified by an independent 

 method. Aqueous solutions of monochloracetic acid of 

 various concentrations were enclosed in scaled glass tubes 

 and heated until the crystals had completely dissolved. 

 The temperatures at which the solutions re-crystallised 

 spontaneously as either a, j3, or 7 crystals were found to 

 agree with the temperatures at which the corresponding 

 solutions passed from the metastable to the labile state as 

 determined by the previous experiments. The three solu- 

 bility curves for the three modifications of monochloracetic 

 acid have also been obtained. The second part of the 

 paper deals with mixtures of monochloracetic acid and 

 naphthalene. These substances Cady describes as forming 

 mixed crystals and possessing a minimum, or eutectic, 

 freezing point {Journ. Phys. Chem., 1899, iii.. 127). In a 

 long series of experiments, however, of which an account 

 is given, there has never been any indication of the forma- 

 tion of mixed crystals. The melting and freezing points 

 of a large number of mixtures were carefully determined, 

 but in no case was there found to be any appreciable 

 difference between these points. The study of the crystal- 

 lisation of these mixtures therefore yields results, similar 

 to those obtained for salol and betol (Proc. Roy. Soc, .A, 

 Ixxix., 1907), a new feature being introduced by the e.xist- 

 cnce of the three modifications of monochloracetic acid. 

 Four solubility curves have been traced, i.e. the solubility 

 curve for naphthalene in monochloracetic acid, and the 

 three solubility curves for the modifications a, 0, and 7 

 of monochloracetic acid in naphthalene. Each of the latter 

 meets the naphthalene solubility curve in a eutectic point, 

 thus giving three eutectic points. Similarly, four super- 

 solubility curves for these mixtures have been determined, 

 giving the temperatures at which naphthalene and the 

 three modifications of the acid crystallise spontaneously. 

 These curves intersect in three hypertectic points, showing 

 the highest temperature at which naphthalene and each 

 modification of the acid respectively can cryst.nllise spon- 

 taneously together. The four solubility and four super- 

 solubility curves when plotted on» a diagram show that in 

 a mixture of two substances, of which one exists in three 

 modifications, eight freezing points may be exhibited bv a 

 cooling mixture. — .\n apparatus for measurements of the 

 definin.rt power of objectives : J. de Graaff Hunter. The 

 genera! principle of the method of measurement employed 

 may be stated as follows. The image of a knife-edge 

 formed bv a photographic lens, when viewed with a micro- 

 scope, will no longer appear as a sharo edge ; the illumina- 

 tion of the bright portion of the field will onlv gradually 

 fade awriy to compli-te darkness .-it some position within 



