SURFACE TENSION OF SERUM : IV. ACTION OF TEMPERATURE.

1. The surface tension of pure serum, heated at 55°C., decreases progressively and regularly until the serum coagulates. A drop of 8.2 dynes was observed in 168 hours. The mean drop was 5.7 dynes in 120 hours and 4 dynes in 96 hours. 2. The initial surface tension of solutions of serum at the concentrations 10–1 up to 10–6 is practically not affected by heat, but the time-drop in 2 hours is modified. 3. Each serum seems to react in its own particular way as far as the time-drop is concerned. However, there is a general tendency for the solution to show an increase of time-drop at the concentrations 10–1, 10–2, 10–3 and 10–5, and a decrease at 10–4, when heated at 55°C. a decrease of the time-drop at the concentrations 10–1, 10–2 and 10–3, and an increase at 10–4 when heated at 100°C. 4. Nevertheless, only the changes observed below 10–3 are constant in sign, within 75 or 80 per cent of the cases. The concentration 10–4 seems to correspond to a state of greater instability. This confirms the hypothesis of the existence of a monomolecular layer at that concentration, which was assumed on the basis of the existence of a maximum drop at 10–4. Should this be true, and provided the principle of Gibbs could be transformed so as to be applicable to mixed solutions of colloids and crystalloids, an idea of the size, or at least of one of the dimensions of the molecules or group molecules composing the serum could probably be obtained. 5. 1 drop of the solutions at 1:10 evaporated on glass and examined under the microscope shows the marked differences brought about by heating at different temperatures

SPONTANEOUS DECREASE OF THE SURFACE TENSION OF SERUM. I

1. Over 3,000 measurements of surface tension of sera have been made with the ring method, and they have yielded a new phenomenon, the spontaneous and rapid decrease of the surface tension of a serum in function of the time. 2. Generally, after 10 minutes the surface tension reaches a value which is practically constant. At least, the decrease is very much slower. After stirring, a rise occurs and a similar phenomenon takes place; but stability is not obtained as rapidly, requiring about 25 minutes. By stirring again, the same thing happens repeatedly, the slope of the curve being less marked each time, the rise in surface tension being slightly below each previous value, and the phenomenon undergoing a sort of damping. 3. An equation was established which expresses the experimental facts with an accuracy of about 0.2 per cent. It applies to the whole phenomenon, before and after stirring. It has only one characteristic constant, See PDF for Equation This formula, by simply changing t to c (concentration), expresses satisfactorily in general the phenomenon of adsorption in the surface layer; that is, the decrease in surface tension in function of the concentration. 4. Prolonged heat, at 55°C., and time seem to inhibit this phenomenon. 5. When precipitation occurs in a serum, the bottom of the liquid, which contains the precipitate, has the highest surface tension. When stirred, the surface tension rises a little every time. The upper part, clear, with lower surface tension, shows the reverse phenomenon; after every stirring, the surface tension becomes a little lower

SURFACE TENSION OF SERUM : VIII. FURTHER EVIDENCE INDICATING THE EXISTENCE OF A SUPERFICIAL POLARIZED LAYER OF MOLECULES AT CERTAIN DILUTIONS.

The assumption has been made in preceding papers that, at a given concentration of 1:10,000, in the vessels used in our experiments, a monomolecular oriented layer was formed. Such a layer might be supposed to prevent the free escape of water molecules from the surface into the air, at least to a certain extent. In order to check this assumption, the rate of evaporation of solutions of serum at different concentrations was measured. It was found that, under the conditions of the experiments, in a progression of dilutions from 10–1 to 10–6, the slowest evaporation took place at a concentration of 1:10,000. In a few cases (less than 20 per cent), evaporation was slower at a different concentration, but always within the same range (between 10–3 and 10–5), not far from 10–4

SURFACE TENSION OF SERUM : XIII. ON CERTAIN PHYSICOCHEMICAL CHANGES IN SERUM AS A RESULT OF IMMUNIZATION.

1. The injection of antigen into an animal determines a gradual change in the blood fluid which finds expression in two physicochemical manifestations that can readily be followed, namely a decrease in the static value of the surface tension of serum solutions, and a special form of crystallization when serum diluted with isotonic sodium chloride solution is allowed to evaporate under certain conditions. 2. The change in the blood is at a maximum around the 13th day after the first antigen injection, and decreases progressively thereafter until it can no longer be observed, which is usually around the 30th day. 3. The change follows the same course, whether a single large injection of antigen is made, or many smaller ones. It begins at the same time in either case, it comes to a maximum after the same period, and in its subsequent course it is not affected by the reinjection of antigen. The manifestations of the change would appear to be independent of the presence of antigen in the circulation. 4. The mean length of the protein molecules of the immune serum obtained after the injection of the antigen dealt with is little if at all different from that of the protein molecules of normal serum. 5. It is possible that this reaction is independent of the antibody formation

CICATRIZATION OF WOUNDS : X. A GENERAL EQUATION FOR THE LAW OF CICATRIZATION OF SURFACE WOUNDS.

1. The law of cicatrization, of surface wounds may be expressed by an exponential formula in which the two coefficients may be determined. 2. A simple relation exists between these coefficients and the index, i, of cicatrization, previously established in function of the age of the patient and of the area of the wound. 3. The proposed equation with a simplified exponent, reduced to a single coefficient, expresses satisfactorily the phenomenon of contraction

SURFACE TENSION OF SERUM : VI. THE STUDY OF IMMUNE SERUM. TIME-DROP AND INITIAL VALUE OF SURFACE TENSION.

1. The initial surface tension of serum or serum solutions is not affected systematically by the presence of antibodies in the serum. On the contrary, the time-drop in 2 hours is always increased, from 25 to 100 per cent. 2. It is extremely important, in order to demonstrate these phenomena, that the greatest care be taken regarding the cleanness of the vessels and the purity of water and NaCl. 3. It is equally important to use a device, for example such as is pictured in this paper, capable of preventing the jarring and shaking of the liquid. 4. The value of the time-drop of a normal, healthy serum is never higher than 10 dynes. Should it be higher, the serum must not be used for immunity experiments

SURFACE TENSION OF SERUM : III. RECOVERY AFTER LOWERING BY SURFACE-ACTIVE SUBSTANCES.

1. The equilibrium of the serum corresponding to its normal minimal surface tension is as stable and difficult to break, under ordinary conditions, as the osmotic tension equilibrium. The addition of a strong surface-active substance (sodium oleate, glycocholate, or taurocholate), will not lower it definitely, unless the substance is present in large amounts and in solution. After the first rapid drop has occurred, a process of recovery takes place, which brings back the normal surface tension in a short time (from 2 to 6 minutes in the case of pure serum). As a drop in the surface tension of the serum of animals may be very injurious to the red cells, this process of recovery is a normal one of defense in all cases in which surface-active substances (bile) are set free in the blood. 2. When diluted, the serum shows the same phenomenon to a smaller extent; the time of recovery is very much longer and the final surface tension is always lower than the original value. At a dilution of 1/10,000, no recovery takes place, the dilution being too high to overcome the lowering action of 1/10,000 of sodium oleate. 3. The recovery is stronger when the surface-active substance is added powdered or in a highly concentrated solution, and not stirred. 4. The recovery does not seem to be inversely proportional to the concentration of sodium oleate, when added superficially. Doubling the concentration at 1/2,000, for example, gives the same curve of recovery. This happens under certain conditions; namely, when the liquid is not stirred after the addition of sodium oleate. 5. This recovery is due to a purely physical phenomenon, namely adsorption, and is not specific for the serum. Other colloidal solutions, such as gum arabic, egg albumin, gelatin, and silver and gold sols, show it, only to a smaller degree. The process of recovery follows a logarithmic law in all cases, expressed by an equation of the form See PDF for Equation 6. Temperature affects this phenomenon. At first it enhances it, but finally decreases it. This would seem to connect the loss of the property of the serum known as complement in a serum with a modification of the physical properties of this serum. This phenomenon is being investigated further