Vol. XXII. No. 8.] 



POPULAR SCIEIsrCE E"EWS. 



115 



important part of the city. But the Municipal 

 Council is more occupied with politics, which are 

 not its business, than with the hygienic conditions 

 of Paris, which are part of the business which it 

 is appointed for. However, under the pressure 

 of public opinion, endeavors are being made to 

 purchase new springs or rivers, and to bring more 

 pure water to the city. 



The progress of saccharin is becoming a mat- 

 ter of attention for the French government. A 

 good quantity of sugar is made in France out of 

 turnips, and the government feels it must in some 

 manner protect this industry. The Minister of 

 Agriculture proposes that some tax should be levied 

 on the new sugar, which is gaining considerably in 

 favor, as might be expected. 



Some days ago, for the first time, a young lady 

 has graduated Doctor of Science in the antique 

 Sorbonne. Her thesis is good enough, although in 

 no manner remarkable, and won for her the com- 

 pliments of the jury. Frenchmen are always gal- 

 lant with ladies, and the ladies know it, and take 

 advantage of the weakness. 



A LONG and important discussion has just been 

 carried on, before the Paris Academy of Medicine, 

 concerning leprosy and its etiology and conta- 

 giousness. Two of the best dermatologists of Paris 

 have taken part in the debate, — MM. Besnier and 

 Vidal, — and also a very experienced physician of 

 the naval corps. Dr. Leroy de Mericourt. They 

 have summed up all the facts known at present con- 

 cerning the disease in Europe as well as abroad, in 

 present and in past times; the documents from 

 India, Canada, and the Sandwich Islands have been 

 amply examined and discussed : and, as usual, the 

 opinions differ. Besnier and Vidal are contagion- 

 ists, and believe the Hansen bacillus to be the cause 

 of the di.sease. M. de Mericourt believes more in 

 heredity than in contagion. Each produces facts 

 in favor of his own theory. We cannot much won- 

 der at this, considering how very small is the 

 number of theories, or even facts, that are really 

 recognized by the whole of the persons that are 

 competent to give a judgment thereon. It only 

 shows how much remains to be done before we are 

 in possession of some positive and undisputed facts, 

 and of a good explanation of the same. 



It is hoped, in scientific circles, that in the 

 course of next year, during the great Exhibition, — 

 if it comes off, and if no war or other trouble pre- 

 vents it from being opened, — an international meet- 

 ing of physiologists may be held in Paris. It is the 

 Paris Socidt^ de Biologic that has the credit of 

 having raised the question, and we hope the scheme 

 may be a successful one. Physiology is yet a grow- 

 ing science, and much remains to be done in its 

 sphere; and an annual meeting of physiologists 

 would certainly prove beneficial to the interests 

 of the science they have embraced. A committee 

 is at present engaged in the study of the means 

 by which the meeting might be decided. Apropos 

 of the Exhibition, the Eiffel tower is progressing 

 favorably. It attains at present a hundred meters, 

 — the third of the height that it is to obtain. No 

 particular difficulties seem to have been met with 

 so far, at least, none have been spoken of. 



Professor Grancher of the Paris Medical 

 School has recently communicated an interesting 

 paper concerning the influence of hydrofluoric 

 acid on tuberculosis. This acid was proposed 

 some time ago as a useful agent in the treatment 

 of pulmonary tuberculosis, it being recommended 

 that the patients should inhale air containing 



vapors of this acid. Many physicians have tried 

 this system, and reported the results of their ex- 

 periments in various manners, but generally in an 

 unfavorable one. Professor Grancher, from a num- 

 ber of experiments, draws the conclusion that 

 hydrofluoric-acid vapors do not certainly kill the 

 tuberculosis bacillus, but may in a marked man- 

 ner diminish the infectious properties of the bacil- 

 lus, which is much attenuated. M. Grancher 

 remarks that hydrofluoric acid is very well tolerated 

 bj' patients, and that, such being the case, this 

 method of treatment is a useful one, although it 

 does not destroy the obnoxious bacilli. Professor 

 Grancher's paper will be found in the Proceedings 

 of the Sociele de Biologie (May, 1888), and may 

 prove useful to physicians desirous to see how his 

 experiments (on animals) have been conducted. 



Professor le Denter recently showed, at a 

 meeting of the Paris Academy of Medicine, an 

 interesting case. It is that of a man whose ster- 

 num and part of superior ribs were entirely gone, 

 through bone tuberculosis. In order to put a stop 

 to the abscesses that were in progress, M. le Denter 

 removed all the diseased parts of the bones, and 

 the operation fully succeeded. It had, besides 

 preserving the patient's life, the advantage of ren- 

 dering the man a very interesting object of study 

 for physiologists. The whole of the inferior two- 

 thirds of the sternum being removed, and also part 

 of the anterior extremities of the corresponding 

 ribs, the result is, that the base of the heart and 

 part of the aorta are very accessible to physiological 

 investigation. This investigation has been carried 

 out, through the methods at the disposal of modern 

 physiology, by Dr. H. de Varigny, under Professors 

 Chauveau and Richet's supervision; and the result 

 is, that very fine graphic representations of the 

 aorta pulsation have been obtained, which are quite 

 identical with those obtained on higher animals. 

 Details will be found in the Proceedings of the 

 Socie'le de Biologie and in the Centralblalt fur Physi- 

 ologie. H. 



Paris, June 20. 



— t — 



TRAP-DOOR SPIDERS AND THEIR NESTS. 



In the hotter parts of the earth the threads spun 

 by spiders are often of considerable strength and 

 toughness, and in some cases are sufficiently strong 

 to strike off the hats of passing travellers, or to be 

 woven in looms, like the fibres of the silkworm. 



All the trap-door spiders are remarkable for the 

 great strength of their webs, which are used, not 

 for the capture of prey, but for the strengthening 

 of their earthen homes. The silk is mostly yel- 

 lowish, and so tough that a nest may be removed 

 without any danger of damaging it ; and the silk is 

 so strong, that, even when the earth has been dried 

 and wholly removed, it will bear a considerable 

 strain without breaking, and can be drawn over 

 the finger like a glove. Up to this point the bur- 

 I'ow possesses no advantage over that of the bird- 

 spider, being a simple silk-lined tube. But the 

 spider now sets to work at the construction of a 

 door by which the opening may be liot only closed, 

 but concealed. 



Guided by instinct, it weaves a circular web 

 rather less than the diameter of the burrow, and 

 works into it a quantity of earth. This process is 

 repeated until the spider has constructed a circular 

 plate of alternate layers of web and earth, nearly 

 twice the thickness of a penny, and slightly conical. 

 Eight or ten layers are employed in the manufac- 

 ture of the plate. A small portion of this plate is 

 attached to the lining of the burrow; the webs, in- 

 deed, of the plate being woven into those of the 

 lining, and being a continuation of them. 



The plate, therefore, forms a door with a silken 



hinge; and so accurately is it constructed, that, 

 when it is closed, the upper surface is exactly level 

 with the ground. It will be seen, therefore, that 

 the aperture is effectually closed ; but there are yet 

 two points in the structure of the trap-door which 

 must be noticed. In the first place, the spider takes 

 care to cover the upper surface with earth exactly 

 resembling the soil in which the burrow is sunk, 

 even imitating the irregularity and roughness with 

 astonishing fidelity, and fixing lichens, moss, or 

 even leaves, on it, just as the chaffinch does on its 

 nest. So perfectly is this done, that to discover a 

 trap-door is almost impossible. 



Strangers, when sitting on a bank, are often as- 

 tonished at seeing a circular piece of earth lifted 

 near them, the jaws and legs of a spider partly 

 protruded, and quickly withdrawn when the in- 

 truder is seen. So rapidly does the spider pass back 

 again into its burrow, and shut the door after it, 

 that the movement has been aptly compared to that 

 of a cuckoo in a clock. Even when the eye has 

 been thus directed to the exact spot, it is not easy 

 to find the door. If, hoyever, it be found, and an 

 attempt be made to open it, a tolerably strong re- 

 sistance will be experienced. This is caused by 

 the inhabitant, which holds firmly with its forelegs 

 to the door, and hind legs to the lining of its web, 

 and resists as long as it can. So firmly does it 

 retain its hold, that, when the nest has been pulled 

 out of the soil and torn asunder, the spider has 

 come away with the upper portion, still holding the 

 door against the foe. The marks thus made by 

 the spider's claws may frequently be seen, especially 

 in the doors of old nests, where frequent use has 

 worn away the material. 



The second point of interest in the trap-door is 

 the mode in which it is fixed. The spider always 

 chooses a sloping surface for its burrow, and the 

 hinge is always placed upon the highest point ; so 

 that, when the spider issues forth, the door is self- 

 acting, and shuts by its own weight. 



The nest of a trap-door spider, (Ctenizanidulans) 

 found in Jamaica, bears a curious resemblance to 

 a very small yellow stocking; and the likeness is 

 increased by the fact that in most cases the spider 

 does not content itself with a single tube, but makes 

 the last inch or two of the end at an angle just like 

 that of a stocking-foot. The reason for choosing 

 this form is rather doubtful. At one time it was 

 thought that the spider altered the course of the 

 burrow in consequence of coming across some 

 obstacle, such as a pebble or root ; but, as the bend 

 invariably occurs at the same place, it is evidently 

 intentional, and not accidental. This nest appears 

 to be of the " cork " type 



In the British Museum there is a remarkable 

 example of a burrow with two trap-doors, — one in 

 the usual place at the entrance, and the other an 

 inch or two below it. The reason for this duplicate 

 door was easily discovered. The nest had been 

 made in cultivated ground. Earth had been 

 thrown over the mouth of the burrow, and buried 

 it. The inmate had therefore burrowed upwards 

 until it had made its way into the open air, and 

 had then constructed a second door. 



It must be remembered that only the female 

 spiders live in these nests, the males being very 

 rarely found. The young spider, after quitting 

 the nest of its mother, builds an exact copy of it 

 in miniature, -aud as it grows, gradually enlarges 

 its nest. In the wafer-doors the layers of silk and 

 earth thus added are visible, but are better seen 

 from the cork doors, and in these they may often 

 be separated. 



If the top part of the tube, with the lid, be re- 

 moved, it will be found, on returning to the same 

 spot in a day or two, that the spider has furnished 

 a new door to the tube. The spiders are nocturnal 



