As a secondary function we may recognize, in certain cases, the power of closing wounds, which results from the rapid coagulation of exuded latex in contact with the air.
This " coagulation " leads to the formation of the river-sludges that form deltas.
" Serumalbumin," or " blood-albumin," possibly C450H720N116S60140,, occurs in blood-serum, lymph, chyle, milk, &c.; its coagulation temperature is about 67°.
Fibrinogen is insoluble in water, but soluble in salt solutions; it has three different coagulation temperatures, 56°, 6 7°, 75°.
Fibrin, produced from fibrinogen by a ferment, is a jelly-like substance, coagulable by heat, alcohol, &c. The muscle-albumins include " myosin " or paramyosinogen, a globulin, which by coagulation induces rigor mortis, and the closely related " myosinogen " or myogen; myoglobulin and myoalbumin are also found in muscles.
If a certain minimum charge must be collected in order to start coagulation, it will need the conjunction of 6n monovalent, or 3n divalent, to equal the effect of 2n trivalent ions.
If the latex is warmed or an acid, an alkali or astringent plant juice is added to it, " coagulation " usually takes place more or less readily, the caoutchouc separating in solid flakes or curds.
The efficacy of heat or of an acid, an alkali or other agent in promoting coagulation depends on the character of the latex, and varies with that obtained from different plants.
When exposed to air the latex gradually undergoes putrefactive changes accompanied by coagulation of the caoutchouc. The addition of a small quantity of ammonia or of formalin to some latices usually has the effect of preserving them for a considerable time.
The nature of the coagulation is not yet completely understood.
It has been compared with that of milk and of blood, which depend essentially on the coagulation or separation in curds of a proteid or albuminous substance, such as takes place when white of egg is warmed.
There is, however, reason to believe that the coagulation of latex into rubber is not mainly of this character.
The globules in the latex are liquid, and the phenomenon of coagulation would seem to consist in the passage of this liquid into solid caoutchouc through the kind of change known as polymerization or condensation, in which a liquid passes into solid without alteration of composition or by condensation with the elimination of the elements of water.
The effect of chemical agents in producing coagulation are in consonance with what is known of other instances of polymeric or condensation changes, whilst the fact that the collection of globules separated by creaming after thorough washing, and therefore removal of all proteid, is susceptible of solidification into caoutchouc by a merely mechanical act such as churning, strongly supports the view that the character of the change is distinct from that of any alteration which may occur in the proteid constituents of the latex.
Be feared that immature trees are often tapped and their latex mixed with that of older trees before coagulation, thus forming.
The point of next importance is the coagulation of the latex so as to produce rubber in the form and of the quality required by the manufacturer.
The primitive methods of coagulation and curing practised in S.
The coagulated rubber separates as a mass of spongy caoutchouc. If the coagulation has been effected in shallow dishes, the rubber is obtained in a thin cake of similar shape known as a " biscuit."
In two or three minutes coagulation takes place, and the rubber is then exposed to the air on sticks, and allowed to drain for eight days.
The globules in the latex, however, consist more probably of a distinct liquid substance which readily changes into the solid caoutchouc. The coagulation of the latex often originates with the " curding " of the proteids present, and this alteration in the proteid leads to the solidification of the globules into caoutchouc. The latter, however, is probably a distinct effect.
There is no feasible method at present known of preventing the inclusion of the resin of the latex with the rubber during coagulation, and although the separation of the resin from the solid caoutchouc by means of solvents is possible, it is not practicable or profitable commercially.
Recent investigations point to the conclusion that the immediate cause of the arrest of vitality, in the first place, and of its destruction, in the second, is the coagulation of certain substances in the protoplasm, and that the latter contains various coagulable matters, which solidify at different temperatures.
And it remains to be seen, how far the death of any form of living matter, at a given temperature, depends on the destruction of its fundamental substance at that heat, and how far death is brought about by the coagulation of merely accessory compounds.
The ferment thus set free brings about the coagulation of the serum, which acts as a protective and temporary scaffolding to the injured tissues.
The second operation is the coagulation of the albumen, and the separation of it with other impurities from the Maceration or Imbibition.
Natural arrest of haemorrhage arises from (I) the coagulation of the blood itself, (2) the diminution of the heart's action as in fainting, (3) changes taking place in the cut vessel causing its retraction and contraction.
Some of these colloids dissolve in water or other liquids to form solutions called by Graham hydrosols; Graham named the solids formed by the setting or coagulation of these liquids hydrogels.
The power of coagulation of colloids shown by electrolytes depends in a curious manner on the chemical valency of the effective ion.
If we assume that a certain minimum electric charge must be brought into contact with a group of colloid particles to produce coagulation, twice as many univalent ions must collect to produce the same effect as a number of divalent ions, and three times as many as an effective number of trivalent ions.
But recent experiments have shown that the simple theory of coagulation here outlined needs amplification in certain directions.
Brodie, in ascertaining the physiological properties of nucleo-proteids, found that when they were intravascularly injected into pigmented rabbits, coagulation of the blood resulted, but of the eight albinoes which they used, none clotted.
Pickering showed that the three synthesized colloids of Grimaux in the same way produced coagulation in pigmented animals, but failed to do so in albinoes.
Pickering, still later, showed, in the case of four Norway hares, two of which were injected while in their pigmented or summer coat, and two while in their albino or winter coat, that coagulation occurred in the former cases but not in the latter.
But about 7% showed an exceedingly limited coagulation, in which the clot was colourless and flocculent, and confined to the heart.
Moreover, it was found that all the failures of coagulation occurred when the nucleo-proteid used was obtained from pigmented animals.
In the intravascular coagulation experiments above described, all the rabbits were carefully weighed, and the amount of nucleoproteid injected until coagulation occurred was measured.
P. Mudge, "Intravascular Coagulation and Albinism, Preliminary Note," Proc. Phys.
The media are used either in a fluid or solid condition, the latter being obtained by a process of coagulation, or by the addition of a gelatinizing agent, and are placed in glass tubes or flasks plugged with cotton-wool.
To mention examples, blood serum solidified at a suitable temperature is a highly suitable medium, and various media are made with extract of meat as a basis, with the addition of gelatine or agar as solidifying agents and of non-coagulable proteids (commercial " pep tone ") to make up for proteids lost by coagulation in the preparation.