692 



UNDERGROUND TEMPERATURE. 



to an open abscess, and abscesses are always 

 opened by an instrument which carefully ex- 

 cludes the air from contact with the wound. 

 The instrument should, of course, be scrupu- 

 lously clean; but it can be made perfectly 

 clean in an atmosphere of dust only by being 

 made as hot as its temper will bear. This is 

 not done, and therefore inflammation often 

 sets in after the first operation ; rapid putre- 

 faction accompanies it, and the pus, which at 

 first showed no traces of animal life, is now 

 found to be full of active little organisms 

 called vibrios. Prof. Lister, from whose 

 letter this fact is derived, contends that this 

 astounding development of animal life is due 

 to the entry of germs into the abscess during 

 the first operation, and their subsequent de- 

 velopment by favorable circumstances. Hay 

 fever is another case in point. 



The celebrated physiologist Helmholtz suf- 

 fers from the 20th of May till the end of June 

 from a catarrh of the upper air-passages, and 

 he has found that, during this period, and at 

 no other, his nasal secretions are peopled by 

 these vibrios. They nestle in the cavities of 

 the nose, and a sneeze is necessary to dislodge 

 them. These are uncomfortable statements, 

 but, if the germ-theory is found to be true, it 

 will give definiteness to our efforts to stamp 

 out disease : and it is only by some definite 

 efforts under its guidance that its truth or 

 falsehood can be established. Dr. Tyndall 

 drew certain practical conclusions from the 

 survey of these two classes of facts. The dust 

 cannot be blown away by ordinary bellows, 

 since the air they send out is equally full of 

 the particles. But fill the nozzle with cotton- 

 wool, not too tightly pressed, and the air is 

 filtered, and, being then blown across the beam 

 of light, forms a clean band of darkness, like 

 the air from the spirit-lamp, or from the heated 

 platinum wire. This was the filter Schroeder 

 used in his experiments on spontaneous gener- 

 ation ; it was also turned to account in the ex- 

 cellent researches of Pasteur. Since 1868, Prof. 

 Tyndall has constantly employed it himself. 



The most interesting of all illustrations of 

 this filtering proces's is furnished by the human 

 breath. Fill the lungs with ordinary air, and 

 breathe through a warm tube warmed to pre- 

 vent the condensation of the watery particles 

 across the beam of light which is revealing 

 the dust-particles in the air. The particles 

 move with the moving air, but the current 

 from the lungs shows, at first, as many particles 

 as the ordinary atmosphere. Gradually, how- 

 ever, the dust-particles clear away from the 



course of the breath, and, by the time you 

 have completed your expiration, the expired 

 air cuts a sharp black line through the motes 

 in the sunbeam. The air has left its dirt in 

 the lungs, and the last portions of the expired 

 breath are free from floating dust. But empty 

 the lungs as far as possible, and then inhale a 

 deep breath through a handful of cotton- wool, 

 and, on expiring the air the same way, it cuts 

 a black line through the sunbeam at once. 

 Place the tube below the beam and blow up- 

 ward, and the air rises through the dancing 

 particles like black smoke, just as it did from 

 the heated surfaces on which the dust was 

 burned. The cotton-wool has completely in- 

 tercepted the floating matter on its way to 

 the lungs, and, as no dust was inhaled, none 

 is exhaled. 



Here, then, is the philosophy of an instinc- 

 tive habit of medical men. In a contagious 

 atmosphere the physician puts- his handker- 

 chief to his mouth, and inhales through it ; in 

 so doing he keeps back the floating germs. If 

 the poison were a gas, it could not thus be in- 

 tercepted. Dr. Bence Jones repeated Dr. Tyn- 

 dall's experiment with a silk handkerchief, 

 with a similar but less-marked result. Cotton- 

 wool is, in fact, the best and surest filter, and 

 a physician who wants to hold back from the 

 lungs of his patient, or from his own lungs, the 

 germs by which contagious disease is said to 

 be propagated, will employ a cotton-wool respi- 

 rator. "After the revelations of this evening," 

 concluded Dr. Tyndall, " such respirators must, 

 I think, come into general use as a defence 

 against contagion. In the crowded dwellings 

 of the London poor, where the isolation of the 

 sick is difficult, if not impossible, the noxious 

 air around the patient may, by this simple 

 means, be restored to practical purity. Thus 

 filtered, the attendants may breathe the air un- 

 harmed. In all probability, the protection of 

 the lungs will be the protection of the entire 

 system. For it is exceedingly probable that 

 the germs which lodge in the air-passages, and 

 which, at their leisure, can work their way 

 across the mucous membrane, are those which 

 sow in the body epidemic diseases. If this be 

 so, then disease can certainly be warded off by 

 filters of cotton- wool. I should be most will- 

 ing to test their efficacy in my own person ; 

 and time will decide whether, in lung-disease, 

 also, the woollen respirator cannot abate irrita- 

 tion, if not arrest decay. By its means, so far 

 as the germs are concerned, the air of the 

 highest Alps may be brought into the cham- 

 ber of the invalid. 



IT 



UNDERGROUND TEMPERATURE. The 

 temperature inside the earth has often been a 

 matter of speculation. Mr. G. J. Symons, the 

 well-known authority on rain and rain-fall, has 

 been investigating the subject. He has carried 



on his experiments at Hampstead. A well 

 was sunk there many years ago into the chalk 

 to the depth of between 500 ft. and 600 ft. for 

 the water-supply, and the demand exceeding 

 the supply, ail Artesian bore was made through 



