December 22, 192 1] 



NATURE 



539 



case of a particular tumour which was found 

 on removal to be only in part malignant, but when 

 a culture was made of the epithelium of the 

 normal part the cells, deprived of the influence of 

 their surrounding tissues, gave rise to daughter- 

 cells similar to those of the malignant growth. 



Again the power of survival of transplanted 

 organs shows how complex is the variety of 

 factors distinguishing one individual from 

 another even within the same species. Prof. 

 Leo Loeb has made a large number of experiments 

 of this kind in the United States, and finds, in 

 agreement with other workers, that tissues trans- 

 planted into another species die more or less 

 rapidly ; if put into another individual of the 

 same species they also die in the end, but not so 

 soon as in the first case. If simply moved into 

 another part of the body of the same individual 

 they survive and grow. In some cases they may 

 survive in the body of an individual closely related 

 to that from which the tissue was taken — as, for 

 example, a brother. Now while Prof. Loeb 

 assumes that the results are chiefly due to the 

 giving off by the cells of specific chemical entities 

 which differ from individual to individual, we must 

 remember that we have no actual proof of this. 

 It is perhaps well to be cautious until the specific 

 properties are shown to be of a chemical nature. 

 An interesting fact is that the specificity spoken 

 of reaches this high state of development only in 

 the higher vertebrates, and is much less manifest 

 in their embryonic stages. 



The hypothesis that all constituent cells of an 

 organism give off internal secretions is clearly at 

 the basis of hormone theories of heredity, such as 

 that associated with the name of J. T. Cunning- 

 ham. However inaccessible to influence of other 

 kinds, it cannot be denied that the germ-plasm 

 must be exposed to the action of substances in 

 solution in the blood. The experiments of 

 Stockard show that the germ-plasm in guinea- 

 pigs is altered for several generations by the 

 action of alcohol on the original parents. The 

 removal of an organ, such as the tail, containing 

 merely tissues abundantly present elsewhere would 

 not be expected, on this hypothesis, to have any 

 effect capable of hereditary transmission. 



The internal secretions, especially those affect- 

 ing growth, have an obvious resemblance to the 

 accessory food factors or vitamins ; but these have 

 to be supplied to animals from the outside, ulti- 

 mately from vegetable food, since plants only are 

 able to make them. In neither case, however, 

 do we know the chemical nature of the substance 

 concerned. It may turn out that we have to do 

 with minute traces of metallic elements, perhaps 

 some of the rare metals. In that connection we 

 are reminded of the necessity for zinc, in ex- 

 tremely small amounts, for the optimal growth 

 of the mould Aspergillus. Certain of the endo- 

 crine organs may, indeed, have the function of 

 supplying in an active or utilisable form some 

 particular element, as appears to be the case with 

 the thyroid gland in relation to iodine. 



Leader" Cables for Aircraft. 



t'OR some time past experiments have been in 

 ■^ progress in adapting to the purposes of aerial 

 navigation the ' ' leader ' ' cable system now success- 

 ; fully used in connection with shipping. Various 

 ; tests made in this country revealed that a marine 

 1 installation is of little use to aircraft, as no signals 

 1 were received from the cable whilst an aeroplane 

 (j was over the submerged part of it. But when the 

 ii land portion of the cable was reached the signals 

 ijit gave out were heard easily in the machine 

 lithrough an ordinary telephonic receiver. If the 

 f.cable be laid above ground, or suspended from 

 iipoles, the '' leader '"' system can be employed 

 ias successfully to guide aircraft as to guide 

 phipping. The principle is the same in each case, 

 \ though some modifications in applying it are 

 necessary. 



So far as England is concerned, we do not appear 

 to have gone much beyond demonstrating the fact 

 that a " leader " cable for aircraft is a practical 

 proposition. But Lieut. Loth, of the French navy, 

 after devoting a considerable period to investigating 

 the subject, has devised an aircraft " leader " cable 

 which proved highly successful when tried at the 

 Villacoublay aerodrome. This officer is well known 

 for his work in connection with such cables, as he 

 NO. 2721, VOL. 108] 



was largely responsible for laying the marine in- 

 stallation at Brest. His aerial apparatus follows 

 closely upon the lines of that employed in ships. 

 Three receiving coils are fixed on the aeroplane, 

 and the pilot takes in signals by means of 

 *■ listeners," or ear-pieces, in his helmet. When 

 the machine is flying directly above, or parallel to, 

 the cable a strong signal is transmitted to the pilot 

 through the centre coil, and this continues so long 

 as the cable is being " followed." The other coils 

 indicate when the machine is to right or left of the 

 cable, and enable the pilot to '" pick up " the in- 

 stallation. Signals can be heard at an altitude of 

 10,000 ft. and for a mile and a half on either side 

 of the cable. 



In the case of a submarine cable, the area over 

 which sound can be heard is necessarily limited, 

 because a good deal of energy is expended in pro- 

 ducing currents in sea water. In the air no such 

 loss of energy occurs, and therefore the sound-range 

 can be very materially increased. '■ Leader " cables 

 fulfil the same fimction in relation to aircraft as to 

 seacraft by enabling them to find their way home in 

 thick weather or in the dark, and by adopting the 

 system the practice of lighting flares on aerodromes 

 is made unnecessary. 



