12 



NATURE 



[March 4, 1920 



and produced without difficulty from a constituent 

 of the nitrogenous cell structures, which is able 

 to produce a state of the circulation like that 

 present in wound-shock. It was found that the 

 effect was not due to a dilatation of the arterial 

 part of the system, as was known to be the case 

 in the fall of blood-pressure brought about by 

 vaso-motor reflexes. Here the similarity to 

 traumatic toxaemia showed itself again, because 

 it was known that arterial • dilatation was not 

 present in this state. Next, Dale and Richards, 

 by a number of ingenious experiments, were able 

 to localise the effect in the capillaries, which 

 became widely dilated and thus capable of taking 

 up the greater part of the blood in the body, 

 leaving the heart nearly empty, with too meagre 

 a supply to carry on the circulation with any 

 degree of efficacy. It is to be admitted that 

 we have not yet definite proof that it is histamine 

 itself which is responsible for the toxaemia of 

 injury. But that the agent is something which acts 

 in the same way is made clear by the observations 

 that have' been made on wounded men. The 

 determinations of the volume of the blood in 

 circulation, made by N. M. Keith, may be espe- 

 cially mentioned. Keith showed that, in severe 

 cases, it may be reduced to little more than half 

 the normal amount, although scarcely any has 

 actually been lost by haemorrhage. The method 

 used was that of introducing into a vein a known 

 quantity of an innocuous dye which does not pass 

 through the walls of the blood-vessels, and, after 

 a short interval, taking a sample of the blood and 

 finding how much the dye has been diluted. 



If the toxcemia is severe, a second property of 

 the poison shows itself. This is an effect on the 

 walls of the capillaries such that they allow the 

 liquid part of the blood to escape by filtration. 

 In this way the volume of the blood is still further 

 reduced. 



The treatment, in principle, is obvious. 

 Restore the blood-volume. It would appear that 

 when blood has been lost it ought to be replaced 

 by blood. The case of traumatic toxaemia is not 

 so clear at once, because blood has not been 

 actually lost, and it should be possible to keep 

 un an effective circulation by some other liquid 

 until the poison is got rid of and the pooled blood 

 returned to circulation. In fact, as experience 



increased, it was realised that the important 

 matter is to maintain the volume in circulation, 

 whether by blood or other solution. An innocu- 

 ous fluid seemed to serve practically as well as 

 blood, and had the advantage of being always at 

 hand and in as large a quantity as required. 



As to the properties of such a solution, it was 

 soon found that a simple saline solution is very 

 rapidly lost from the circulation and is useless. 

 It is necessary to add to it some colloid with an 

 osmotic pressure, such as gelatin or gum acacia. 

 The colloid does not pass through the walls of 

 the blood-vessels, and its osmotic pressure causes 

 an attraction of water to balance that lost by 

 filtration. Thus, although the slow circulation 

 incidental to a small volume of blood is inade- 

 quate, this very quantity, if diluted to normal 

 volume, is able to serve effectively. Comparing the 

 oxygen carried by the red corpuscles to railway 

 passengers, it will be realised that if we have a 

 limited number of trains, we can carry more 

 passengers in a given time if the velocity of the 

 trains is increased. Animal experiments made by 

 Gasser showed that this is actually the case with 

 the blood. After a loss of blood the injection of 

 gum-saline might even raise the supply of blood- 

 corpuscles to a level beyond what it was before 

 the haemorrhage. 



The general conclusion is that the volume of 

 the liquid in circulation must be kept up to its 

 normal value, whatever this liquid may be. Of 

 course, the number of red corpuscles cannot be 

 allowed to fall below some particular value, and 

 it has been found that about one-quarter of the 

 normal quantity is the lowest compatible with 

 life. If they fall below this, moreover, there is 

 no production of new corpuscles. 



In the later stages of the war gum-saline was 

 largely used in the British, American, and French 

 .Armies, and is reported to have saved many lives. 

 Unfortunately, if too long a time is allowed to 

 elapse before treatment, nothing avails, not even 

 transfusion of blood. Hence the importance of 

 the early use of intravenous injection, and also 

 of removal of the injured tissue by operation. 

 As the war progressed, these procedures were, 

 therefore, pushed more and more forward to the 

 battle area, and with more and more favourable 

 results. 



Characteristics of Pigments in Early Pencil Writing. 



By C. Ainsworth Mitchell. 



JDENCIL pigments may be classified in the fol- 

 ^ lowing groups : (i) Metallic lead or alloys 

 of lead ; (2) graphite cut from the block ; (3) early 

 composite pigments containing graphite, sulphur, 

 resins, etc., but no clay; (4) graphite powder 

 compressed into blocks ; and (5) composite pig- 

 ments containing graphite with clay and other 

 ingredients. These pigments usually show dis- 

 tinctive microscopic characteristics in the marks 

 which they produce. 



NO. 2627, VOL. 105] 



When examined under the microscope with a 

 magnification of about twenty diameters and the 

 light at right angles, ordinary lead shows, in its 

 vertical markings on paper, a series of irregularly 

 distributed patches, uniformly and brilliantly lit up, 

 and marked with regular vertical striations which 

 have the appearance of ridges. In the case of 

 Borrowdale graphite (Fig. i) the vertical lines show 

 relatively few brilliant straight striations (due to 

 siliceous impurities), and when these occur in the 



