THE CRYOSCOPIC METHOD FOR THE DETERMINATION OF "BOUND WATER"

1. The criticisms by Grollman (7) of the cryoscopic method for the determination of bound water as proposed by Newton and Gortner (1) have been considered, and it is pointed out that even admitting the correctness of his contentions does not negative the conclusion that bound water values as determined by the cryoscopic method parallel in a remarkable manner the physiological responses of plants to environmental conditions. 2. A new method of calculating the true freezing point of a solution is proposed. 3. Gum acacia in aqueous sucrose solutions shows positive amounts of bound water to the extent of 0.6 to 0.7 gm. of bound water per gram of gum. 4. Gum acacia in aqueous solutions of KCl and KBr shows slightly negative amounts of bound water, indicating a preferential adsorption of the solute rather than the solvent.     

THE COMPOSITION OF FLUIDS AND SERA OF SOME MARINE ANIMALS AND OF THE SEA WATER IN WHICH THEY LIVE

1. The electrolyte composition, the pH, and freezing points of the fluids of several invertebrates and one primitive chordate are reported. 2. Fluids of the worms, echinoderms, and the clam Venus were isotonic with sea water; fluids of the Arthropoda were hypertonic to sea water. 3. The pH of all fluids was below that of sea water. In the Arthropoda and Myxine less individual variation in pH appeared than in the echinoderms and worms. 4. Ratios of ionic concentrations in the fluid to those in the sea water indicated (1) uniform distribution of ions between the internal and external media for the echinoderms and Venus, (2) differential distribution of potassium and magnesium in the worms; (3) differential distribution of sulfate, magnesium, potassium, and calcium in the Arthropoda; and (4) differential distribution of calcium, magnesium, and sulfate in Myxine. 5. The unequal distribution of ions implies the expenditure of energy against a concentration gradient across the absorbing or excreting membranes, a capacity frequently overlooked in the invertebrates. 6. The sera of the Arthropoda from diluted sea water showed higher concentrations of sodium, potassium, calcium, and chloride ions relative to the respective concentrations in the external medium than in normal sea water, and also showed different orders for those ions. 7. The increase in osmotic pressure of the sera of the animals moving into brackish water is caused by unequal accumulation of sodium, potassium, calcium, and chloride ions. Sulfate and magnesium ionic ratios do not change.     

BOUND WATER IN MUSCLE

1. The amount of free unfrozen water, i.e. water acting as normal solvent, in frog''s muscle at temperatures below the initial freezing-point has been calculated from the vapour pressure isotherm of the muscle. 2. Significant amounts of free water are present at –20°C. The total amount of unfrozen water at –20°C. cannot, therefore, be taken as a measure of the bound water in muscle. 3. The calculated values of free water, when compared with experimentally determined values of total unfrozen water, indicate that the amount of bound water in muscle at various temperatures is small. 4. A temperature considerably below –20°C., roughly between –40° and –60°C., is required to freeze completely the free water in muscle.     

THE DETERMINATION OF ESCHERICHIA COLI I IN SEA WATER

SUMMARY: For the determination of Escherichia coli I in sea water lactose broth frequently gave higher presumptive and confirmed counts than MacConkey's broth. In the presumptive count there were 53 cases where lactose broth gave larger numbers than MacConkey's broth, with 11 equal counts, and only 25 cases with smaller counts ( P =0·00137). After confirmation the corresponding numbers of cases were 39, 10 and 27 ( P =0·134).
In the samples giving most probable numbers (MPN) of less than 100 E. coli /100 ml lactose broth was superior to MacConkey's broth ( P =0·021). At higher MPN values both media were satisfactory, but with highly polluted water MacConkey's broth might give better recoveries due to the suppression of high concentrations of non-coli-aerogenes bacteria.
Samples stored for 24 or 48 hr before testing gave higher presumptive recoveries when examined with lactose broth than with MacConkey's broth, the values for P being 0·028 and 0·0027 respectively.
It appears that lactose broth without inhibitory ingredients could be used with advantage in the examination of sea water.     

THE DETERMINATION OF CHLOROPHYLL a IN WATER CONTAINING SEDIMENT

SUMMARY

The presence of sediment at concentrations of 0,2% by mass in water samples significantly lowered the amount of chlorophyll a that could be measured. Two types of sediment differed in their ability to lower the chlorophyll a concentration. The chemically more active sediment had a marked depressive effect on the chlorophyll a concentration and the relationship between chlorophyll a and cell numbers in the samples was non-linear. It is recommended that the use of chlorophyll a as an indicator of biomass in water containing sediment should be approached with care.     

在年龄结构化动物种群的分析过程中常见的几种错误

分析动物各年龄组的种群数据有助于推断影响动物种群发展趋势的诸因素,而且便于设计出种群层次。然而,在研究近期文献资料时,我们发现存在三种错误。这些错误均可导致非正确的解释。即:1)在生命表分析中,将Sx与lx等同(Sx由各死亡年龄组推导而出,lx为存活率);2)在综合跨年龄组的成雌生育率时,不计算该年龄组的成雌死亡数;3)在用Leslie矩阵计算周限增长率时,以mx取代Fx。我们将探讨上述错误的含义及后果,并提出解决方法。     

SOME FACTORS WHICH INFLUENCE THE OXIDATION OF SULFHYDRYL GROUPS

1. Cyanide inhibits the oxidation of the SH groups of cysteine and denatured egg albumin by the uric acid reagent. 2. At pH 4.8 cysteine is oxidized by the uric acid reagent and by ferricyanide in the presence but not in the absence of added copper sulfate. 3. In neutral solution, the uric acid reagent oxidizes the SH groups of denatured egg albumin in the presence of urea but not in the presence of alkyl sulfate or in the absence of denaturing agents. 4. Ferricyanide oxidizes the SH groups of neutral denatured egg albumin even in the presence of alkyl sulfate or, if precautions are taken to avoid aggregation, in the absence of denaturing agents. 5. In acid solution, ferricyanide does not oxidize the SH groups of denatured egg albumin completely. The oxidation is more complete, however, in the presence of urea than in the presence of alkyl sulfate, and more complete in the presence of guanidine hydrochloride than in the presence of urea. 6. The uric acid reagent which does not oxidize the SH groups of neutral denatured but unhydrolyzed egg albumin in the absence of denaturing agents does, under the same conditions, oxidize the SH groups of egg albumin partially hydrolyzed by pepsin. 7. At pH 4.8 in alkyl sulfate solution ferricyanide oxidizes the SH groups of digested egg albumin more completely than the SH groups of denatured but undigested egg albumin.     

SOME OBSERVATIONS ON THE BACTERIAL CONTENT OF WATER IN WATERCRESS BEDS

SUMMARY: Samples of water flowing into watercress beds had higher bacterial contents during the summer months although this was less marked among samples from deep underground sources. Outlet samples showed higher contents than inlet samples and the bacterial content varied markedly with season, being highest in summer.
The presumptive coli-aerogenes contents at 30°, 37° and 44° also showed a similar seasonal variation among samples from the outlets but the marked inferiority of samples other than from bores was no longer apparent after the water had flowed through the beds. The dominant types were Bact. aerogenes type I, pectate liquefiers, Bact. coli type I, and Intermediate type I.
The importance of the pectate liquefiers was confirmed by plating on pectate gel and by their isolation from these plates and from MacConkey's broth.     

A STUDY OF THE PECTOLYTIC BACTERIAL POPULATION IN SOME FARM WATER SUPPLIES

SUMMARY: Pectolytic bacteria in considerable numbers were detected in samples from farm water supplies. Two media were employed, and quantitative data were obtained, in both cases, but colony counts on sodium pectate-calcium agar poured plates gave higher numbers than a presumptive count in sodium pectate solution. The agar medium also permitted the growth of non-pectolytic bacteria, and the total colony count was higher than that obtained on standard nutrient agar. Presumptive coliaerogenes counts in broth tubes showed that these organisms were, on the average, about four times as numerous as the pectolytic organisms.     

THE "BOUND" WATER OF BIOLOGICAL COLLOIDS: A REPLY

The objection by Bull to the estimation of bound water by ultrafiltration, because of an assumed adsorption of the reference substance, has been found invalid for glucose. No adsorption of glucose by the proteins, casein and gelatin, could be detected. The estimation of the bound water of proteins from the probable surface adsorption of water by proteins leads to only a small value.