480 



NATURE 



[January 8, 1920 



some particular organ only of B may be supplied from 

 A, this organ being cut off from the circulation of B. 

 The details of the procedure cannot be described here, 

 but some recent improvements in the technique may 

 be referred to. The chief difficulty lies in the fact 

 that when the blood comes into contact with anv 

 foreign surface that is wetted by it, such as the glass 

 or india-rubber tubes connecting the two animals, 

 clotting occurs. This may be obviated by making the 

 blood incapable of clotting. A substance extracted 

 from the heads of leeches will do this, but it is at the 

 present time almost impossible to obtain it. Other 

 substances having the same elTect are too poisonous. 

 Since the blood does not clot in the uninjured blood- 

 vessels themselves, H^don in France and Dale and 

 Laidlaw in this country have made use of pieces of 

 vein to connect the blood-vessels required. The latter 

 workers desired only to divert the blood from one 

 vein of an animal into .mother of the same animal, 

 so that no great internal pressure was present, and it 

 was sufficient to pass a short metallic tube (Crile's 

 canula) over each end of the piece of vein, reflecting 

 the ends over the tube and tying them. When this 

 is done, and the tube is introduced into a blood- 

 vessel, the blood comes into contact only with the 

 lining of a normal blood-vessel. Hedon, wishing to 

 connect the artery of one animal with that of another, 

 took a metallic tube long enough to enclose nearly 

 the whole length of the piece of vein and reflected the 

 ends) over this. The vein was thus adequately sup- 

 ported against the pressure of the blood in the arteries. 

 Bazett and Ouinby, in the current issue of the 

 Quarterly Journal of Experimental physiology {yo\. xn.. 

 No. 3), describe a method in which the fact is made 

 use of that if blood is in contact only with a foreign 

 surface not wetted by it, clotting is absent for a long 

 time. They coated the interior of the glass and rubber 

 tubes used with a mixture of paraffin and vaseline, 

 and by interposing a specially constructed stopcock 

 were able to connect the circulation of the two animals 

 or return to normal at will. 



These improvements in the technique of cross- 

 circulation should render it possible to investigate 

 problems hitherto diflicult to solve. There is one dis- 

 advantage in it which must not be overlooked. This 

 is the fact that a fall in the blood-pressure in one 

 animal causes an inflow from the other when there is 

 complete intercommunication between the two. Thus 

 one of the animals may be seriouslv depleted if the 

 low pressure lasts for any length of time. For this 

 reason the production of wound-shock in one animal 

 by the products of tissue-injury of another seems im- 

 possible, because the fall of blood-pressure, which is 

 the most marked symptom of the state, would in itself 

 drain blood from the normal animal and produce a 

 similar state merelv by loss of blood, apart from the 

 action of a .chemical substance. ■ W. M. Bayuss. 



NICKEL-CHROMIUM STEEL FORCINGS. 



TOURING the war there was a considerable develop- 

 ^-^ ment of the use of alloy steels, in particular of 

 those containing nickel and chromium. These uses 

 were of the most varied kinds, not the least important 

 being in the construction of internal-combustion 

 engines used in aircraft, where service conditions are 

 verv severe. It is not surprising, therefore, that 

 difficulty in complying with the specifications was en- 

 countered in manufacture, and much novel experience 

 has been accumulated by technical workers in this 

 field of steel metallurgy. 



At the autumn meeting of the Iron and Steel Insti- 

 tute two important papers relating to this class of 

 steel were presented j one was bv Messrs. .^ndrew, 

 Greenwood, and Green, of the metallurgical research 

 NO. 2619, VOL. 104] 



department of Sir VV. G. .\rmstrong, VVhitworih, and 

 Co. ; the other by Mr. R. H. Greaves, of the research 

 department, Woolwich .Arsenal. It is interesting and 

 significant to note that the latter paper is entitled 

 ".Metallurgical Communication No. i, from the Re- 

 search Department, Woolwich." 



Messrs. Andrew, Greenwood, and Green, who took 

 up the investigation of defects in the final tests of 

 nickel-chromium forgings, have carried out their work 

 in a most thorough and exhaustive way, following 

 up the manufacture of these from the original 

 casting to the finished article. It needs consiiderable 

 courage for the investigators in a works to publish 

 evidence showing manifest defects in the products of 

 the firm's work, and the authors are to be com- 

 mended for their honesty in taking this step. It is 

 but rarely that such cases are met with. 



The manufacture of a hollow forging may be 

 divided broadlv into three distinct sets of operations : 

 casting, forging, and heat treatment The authors 

 emphasise the operation of casting as the most im- 

 portant of all, because any defects present in the 

 ingot, generally speaking, persist throughout up to the 

 final treatment. It is essential that not onlv the metat 

 but also the mould-walls should be clean, and that alt 

 loose sand must be prevented from getting into the 

 mould. .'\s a method of assisting in the achievement 

 of these results, the authors suggest the use of a tun- 

 dish with sloping walls lined with basic material. 

 Thev .say that if the metal were run directly into this 

 from the iron ladle, the sloping walls of basic material 

 would act as a cleanser, since the slag would adheri> 

 to the sides of the dish. The cleansing action would 

 be similar to that brought about with mercury when 

 poured through a paper cone with a fine orifice .Tt the 

 bottom. Thev recommend that ingots should be cast 

 wide-end up, and that the smallest size consistent with 

 requirement.^ should be used. They recommend 

 further a high-ladle, but a low-casting, temperature, 

 since this is found to be advantageous in cleansing the 

 metal. The macrostructure of the ingot is deter- 

 mined bv the temperature and method of casting. 

 High-casting temperatures are to be avoided because 

 thev give rise to excessive segregation, ghost lines, 

 etc.. and coarse crystallisation. 



The authors advise that, after casting, the ingct 

 should not be allowed to cool more than is unavoid- 

 able, but should be solid forged as soon as possible. 

 This breaks up the crystals, thus refining them. It 

 also assists in the diffusion of the carbon and thus 

 renders the mass more homogeneous. The effect is 

 to produce a much stronger material the thermal 

 treatment of which can be undertaken with greater 

 safety. In carrying this out with large forgings, verv 

 slow heating up to the temoerature range. 730-760° C 

 must be adopted. .Above this the rate of heating may 

 be quicker. The. authors suggest further that they 

 have obtained evidence that mechanical work can be 

 overdone, and that the greater the amount the more 

 prone is the tendencv to a laminated fracture. A 

 somewhat similar point was made bv M. Charpy in 

 a recent oaoer published on "The Hot Deformation 

 of Iron and Steel." With regard to the final heat 

 treatment the authors say that the temperature of oil- 

 hardening aopears to make little or no difference to 

 the mechanical properties; the important factor is 

 the time at the temperature in question. This should 

 be as short as oossible, since a prolonged heating even 

 at 8i;o° C. coarsens the grain-size and causes a 

 deterioration in nroperties. 



The paoer bv Mr. Greaves deals with the "temper 

 brittleness " of a nickel-chromium steel containing 

 T,-^ oer cent, of nickel, 06 per cent, of chromium. 

 0-; oer cent., of manganese, and 0-2, ner cent, of 

 carbon. This term is applied to the condition Induced 



