

II E M I S T R Y. 



.- 



I'uunia*- 



' . 



Margurron found tliat 100 part* of sinotia contained 

 about O.71 of soda. 



n (inovia is expoted to a dry atmosphere, it frra- 

 duaUy evap"rate. and a scaly retiduum remains, in winch 

 cubic crystals, and a white saline efflores> appa- 



rrnt. The cub; arr muriate of *oda. One hun- 



dred parts of tinovia contain 1.7.3 ol tliu salt. The sa- 

 line efflorescence in carbonate i>f soda. 



From the analysis of Mr Margueron, it appears that 

 Jinovu it composed of the following ingredients: 

 1 l.Sfi fibrous matter, 

 4-52 albunii n. 

 1.75 muriate of soda, 

 .71 soda, 



.70 phosphate of lime, 

 80. H> water. 



100.00 



SECT. XVIII. Of Semen. 



The peculiar liquid secreted in the testes of males, and 

 destined for the impregnation of females, is known by 

 the name of trmen. 



Semen, when newly ejected, is evidently a mixture of 

 two different substances : the one fluid and milky, which 

 is supposed to be secreted by the prostate glai.d ; the 

 other, which is consid- red as the true secretion of the 

 testes, is a thick mucilaginous substance, in which nume- 

 rous white chining filaments may be discovered. It has 

 a slight disagreeable odour, an acrid irritating taste, and 

 its specific gravity is greater than that of water. When 

 rubbed in a mortar, it becomes frothy, and of the con- 

 sistencc of pomatum, in consequence of its enveloping a 

 great number of air bubbles. It converts paper stained 

 with the blossoms of mallows or violets to a green co- 

 lour, and consequently contains an alkali. 



As the liquid cools, the mucilaginous part becomes 

 transparent, and acquires greater consistency ; but in 

 about twenty minutes after its emission, the whole be- 

 comes perfectly liquid. This liquefaction is not owing 

 to the absorption of moisture from the air, for it loses 

 instead of acquiring wright during its exposure to the 

 atmosphere ; nor i-, it owing to the action of the air, for 

 it takes place equally in close vessels. 



When oxymunatic acid is poured into semen, a num- 

 ber of white flakes precipitate, and the acid loses its pe- 

 culiar odour. These flakes are insoluble in water, and 

 even in acids. If the quantity of acid be sufficient, the 

 semen acquires a yellow colour. Thus it appears that 

 semen contains a mucilaginous substance analogous to 

 that of the tears, which coagulates by absorbing oxygen. 

 Mr Vauquelin obtained from 100 parts of semen bix 

 parts of this mucilage. 



When semen is exposed to the air about the tempera- 

 tore of 60, it becomes gradually covered with a tran- 

 sparent pellicle, and in three or four days drposites small 

 transparent crystals, often crossing each other in such a 

 manner as to represent the spokes of a wheel. These 

 crystals, when viewed through a microscope, appear to 

 be four sided prisms, terminated by very Jong four-sided 

 pyramids. They may be separated by diluting the li 

 quid with water, ard decanting it off. They have all 

 the properties of phosphate of lime. f, after the ap- 

 pearance of these crystal*, the semen be still allowed to 

 remain exposed to the atmosphere, the pellicle on its 

 lurface gradually thickens, and a number of white round 

 bodies appear on different parts of it. These bodies also 

 are phosphate of lime, prevented from crystallizing re- 



ItlMI <lf 



Nature. 



tiun - 



by the too rapid abitrction of moisture. M 

 auquelin found that 100 parts of semen contain three 

 parts of phosphate of lune. If, at this period of the 

 evaporation, the air becomes m;>it, other crystals ap- 

 pear in the semen, which ha- :>errcs of carbo- 



nate of s.xla. The evaporation iK'rs n..t j;o on to com- 

 plete exsiccation, unless at thr ti-n,p< i 7, arid 



when the air is very dry. \V en all ih- moi-.turt is eva- 

 porated, the semrn has lost O.!t ><f it-. \v,i.;ht ; the resi- 

 duum is semitransparcnt like horn, a-.d brittle. 



Thui it appears that semen is composed of the follow- 

 ing ingredients : 



90 water. 

 6 mucilage. 

 S ph isphate of lime. 

 1 soda. 



100 



SECT. X .' X. Of Animal Poisons. 



Several animals are furnished with liquid juices of a Animal 

 poisonous nature, which, when poured into fresh wounds, poison*. 

 occasion the disease or death of the wounded animal. 

 Serpents, bees, scorpions, spiders, are well known ex- 

 amples of such animals. The chemical properties of 

 these poisonous juices deserve peculiar attention ; because 

 it is only from such an investigation that we can hope 

 to explain the fatal changes which they inilti -e m the 

 animal economy, or to discover an antidote sufficiently 

 powerful to counteract their t>anciul influence. Unfor- 

 tuately the task is difficult, and perhaps surpassen our 

 chemical powers. For tlu already made in the 



investigation, we are indebted almost entirely to the la- 

 bours of Fontana. 



1. The poison of the viper is a yellow liquid, which Poison of 

 lodges in two small vesicles in the animal's mouth, die viper, 

 These communicate by a tube with the crooked fan^s, 

 which are hollow, and terminate in a small cavity. When 

 the animal bites, the vesicles are squeezed, and the poi- 

 son is forced through the fanjjs into the wound. 



This poisonous juice occasions the f.ital effects of the 

 viper's bite It has a yellow colour, has no taste ; but 

 wfien applied to the tongue occasions numbness. It has 

 the appearance of oil before the microscope, but it unites 

 readily with water. It produces no change on vege- 

 table blues. 



When exposed to the open air, the watery part gra- 

 dually evaporates, and a yellowish-brown substance re- 

 mains, which has the appearance of gum arabic. In this 

 state it feels viscid like gum between the teeth ; it dis- 

 solves readily in water, but not in alcohol j and alcohol 

 throws it down in a white powder from water. Neither 

 acids nor alkalies have much effect upon it. It does 

 not unite with volatile oils nor sulphuret of potash. 

 When healed it does not melt, but swells, and does not 

 inflame till it has become black. These properties are 

 similar to the properties of gum, and indicate the gum- 

 my n.'ture of this poisonous substance. Fontana made 

 a set of experiments on the dry poison of the viper, and 

 a similar set on gum arabic, and obtained the same re- 

 sults. 



From the late observations of Dr Russel, there is 

 reason to believe that .the poisonous juices of thr other 

 serpents are similar in their properties to those ol the vi- 

 per. 



This striking resemblance between gums at.d the poi- 

 bon ot the viper, two ubtances of so opposite a nature 

 in their ctTecls upon the living body, is a humiliating 



