CHEMISTRY. 



149 



proof of the small progress we have made in the chemi- 

 f '"*' cal knowledge of these intricate substances. The poison 

 of the viper, and of serpents in general, is most hurtful 

 . ^ _ _\ when mixed with the blood. Taken ir.to the stomach it 

 kills if the quantity be considerable. Fontana has as- 

 certained that its fatal effects are proportional to its 

 quantity, compared with the quantity of the blood. 

 Hence the danger diminishes as the size of the animal 

 increases. Small birds and quadrupeds die immediately 

 when they are bitten by a viper ; but to a full sized man 

 the bite seldom proves fatal. 



Ammonia has been proposed as an antidote to the 

 bite of the viper. It was introduced in consequence of 

 the theory of Dr Mead, that the poison was of an acid 

 nature. The numerous trials of that medicine by Fon- 

 tana robbed it of all its celebrity ; but it has been lately 

 revived and recommended by Dr Ramsay as a certain 

 cure for the bite of the rattlesnake. 



Bee and 2. The venom of the bee and the wasp is also a liquid 



was P contained in a small vesicle, forced through the hollow 



tube of the sting into the wound inflicted by that instru- 

 ment. From the experiments of Fontana, we learn that 

 it bears a striking resemblance to the poison of the vi- 

 per. That of the bee is much longer in drying when 

 exposed to the air than the venom of the wasp. 

 Scorpion, 3. The poison of the scorpion resembles that of the 

 viper also. But its taste is hot and acrid, which is the 

 case also with the venom of the bee and the wasp. 

 And spider 4. No experiments upon which we can rely have been 

 tribe. made upon the poii-on of the spider tribe. From the ra- 



pidity with which these animals destroy their prey, and 

 even one another, we cannot doubt that their poison is 

 sufficiently virulent. 



SECT. XX. Of Sncal. 



Sweat. A quantity of matter K constantly emitted from the 



skin ; this mutter is invisible, and is distinguished by the 

 name of pertftttflion, .Several experiments were made 

 by Lavoisier and Seguin .to ascertain its amount. Mr 

 Cruk'kshanks made numerous trials to determine its na- 

 ture, and it has been lately subjected to a chemical ex- 

 amination by Thenaid. 



1. Mr Crukkshai'ks put his hand into a glass vessel, 

 and luted its mouth at his wrist by means of a bladder. 

 The interior surface of the vessel became gradually dim, 

 and drops of water trickled down. By keeping- his hand 

 in this manner for an hour, lie collected 30 grains of a 

 liquid, which pusscsvd all the properties of pure water. 

 On repeating the same experiment at nine in the fvtning 

 (thermometer 62,) he collect' d only 12 grains. The 

 mean of these is 21 grains. But as the hand is more 

 exposed than the trunk of the body, it is reasonable to 

 suppose that the persp;riition from it is greater than that 

 from the hand. Let us therefore take 30 grains per 

 hour as the mean ; and let us suppose, with Mr Cruick- 

 shanks, that the hand is ,' th of the surface of the body : 

 The perspiration in an hour would amount to 1880 grains, 

 and in 24 hours to 43,200 grains, or seven pounds s x 

 ounces troy This is almost double of the quantity as- 

 certained by Lavoisier and Seguin. Hence we may 

 conclude that more matter is perspired through the hand 

 than the other parts of the body, provided Mr Cruick- 

 shank's estimate of the ratio between the surface of the 

 hand and body bf not erroneous. 



He repeated the experiment again after hard exercise, 

 and collected in an hour 48 grains of water. He found 

 also, that this aqueous vapour pervaded his stocking 

 without difficulty ; and that it made its way through a 



shimoy leather glove, and even through a leather boot, Clicm-.cal 

 though in a much smaller quantity than when the leg E 

 wanted that covering. 



2. Besides water, it cannot be doubted that carbon is 

 also emitted from the skin ; but in what state, the ex- 

 periments hitherto made do not enable us to decide. Mr 

 Cruick=.hai ks found that the air of the glass vessel in 

 which his hand and foot had been confined for an hour 

 contained carbonic acid gas ; for a candle burned dimly 

 in it, and it rendered limewater turbid. 



3. Besides water and carbon, or carbonic acid gas, the 

 skin emits also a particular odorous substance. That 

 every animal has a peculiar smell, is well known : the 

 dog can discover his master, and even trace him to a dis- 

 tance, by the scent. A dog, chained some hours after 

 his master had set out on a journey of some hundred 

 miles, followed his footsteps by the smell, and found him 

 on the third day in the midst of a crowd. But it is 

 reei'less to multiply instances of this fact, they are too 

 well known to every one. Now this smell must be ow- 

 ing to some peculiar matter which is constantly emitted; 

 and this matter must differ somewhat either in quantity 

 or some other property, as we see that the dog easily 

 distinguishes the individual by means of it. Mr Cruick- 

 shanks has made it probable that this matter is an oily 

 substance ; or at least that there is an oily substance 

 emitted by the skin. He wore repeatedly, night and day, 

 for a month, the same vest of fleecy hosiery during the 

 hottest part of the summer. At the end of this time he 

 always found an oily substance -accumulated in consider- 

 able masses on the nap of the inner surface of the vest, 

 in the form of black tears. When rubbed on paper, it 

 makes it transparent, and hardens on it like grease It 

 burns with .a white flame, and leaves behind it a charry 

 residuum. 



4. Berthollet has observed the perspiration acid ; and 

 he has concluded that the acid which is presont is the 

 phosphoric : but that has not been proved. Indeed the 

 late experiments of Thenard have proved that the acid 

 in pertpin'd mailer is not the phosphoric, but the acetic. 

 He employed the method practised by Mr Cruick- 

 shanks to collect this matter. Different persons wore 

 cleat, flannel waistcoats next their skin for ten days, the 

 waistcoats had been first washed with soap, then in pure 

 water, then in water acidulated with muriatic acid, and 

 lastly in a great quantity of pure wate. He steeped the 

 waistcoats in hot distilled water, and thus separated from 

 them the perspired matter. The liquid was put into a 

 r-jt,:rt, and concentrated to the consistence of a syrup. 

 The liquid which came over had a disagreeable smell, 

 and reddened infusion of litmus. Kept in an open vessel 

 it retained its transparency, but lost its odour. The 

 residue in ; he retort had no smell. It was strongly acid, 

 and tasted distinctly of common salt, while at the same 

 time an acrid and hot flavour could be distinguished. 

 When evaporated to dryness and strongly heated, the 

 acid which it contained was dissipated or destroyed, and 

 the residue consisted of common salt, charcoal, and mi- 

 nute traces of phosphate of liir.e, and oxide of iron. The 

 same destruction of the acid took r.lafe if it was previ- 

 ously saturated with potash before it was heated to red- 

 ness, and in that casr the potash was converted into a 

 carbonate. When saturated with an alkali, and distilled 

 aloiijr with phosphoric acid, it yielded an acid which 

 potocued ail the characters of the ac 



5. The sn>;ill quai.tily of animal matter which The- 

 nard found in tin- perspired matter, possessed characters^ 

 which induced him to consider it as similar to gelatine in 

 its nature. 



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