500 LIQUID PARTS OF ANIMALS. 



and in nitric acid when assisted by heat, but acetic acid only dis- 

 solves it partially. 



Lime disengages no ammonia from fresh semen, but after that 

 fluid has remained for some time in a moist and warm atmosphere, 

 lime separates a great quantity from it. Hence ammonia is 

 formed during the exposure of semen to the air. * 



When chlorine is added to semen, a number of white flocks 

 separate, and the chlorine loses its smell. If the quantity of chlo- 

 rine be considerable, the semen assumes a yellow colour. 



When semen is exposed to the air about the temperature of 

 60, it becomes gradually covered with a transparent pellicle, 

 and in three or four days deposits small transparent crystals, 

 often crossing each other in such a manner as to resemble the 

 spokes of a wheel. They are four-sided prisms, terminated by 

 very long four-sided pyramids. Vauquelin considered them as 

 crystals of phosphate of lime ; but that salt never crystallizes in 

 four-sided prisms. It is much more probable that the crystals 

 are of ammonia-phosphate of magnesia, which assumes the shape 

 of a rectangular prism with a square base. 



If, after the appearance of these crystals, the semen be still 

 allowed to remain exposed to the atmosphere, the pellicle on its 

 surface thickens, and a number of white round bodies appear on 

 different parts of it. These, according to Vauquelin, are con- 

 cretions of phosphate of lime. They amount, he says, to three 

 per cent, of the weight of the semen. If at this period of the 

 evaporation the air become moist, crystals of carbonate of soda, 

 and doubtless of common salt, appear in the substance. The 

 evaporation does not go on to complete desiccation unless the air 

 be very dry and the temperature at least as high as 77, the resi- 

 due amounts to one-tenth of the semen. It is translucent like 

 horn, and brittle. 



When semen is kept in very moist air, at the temperature of 

 about 77, it acquires a yellow colour like that of the yolk of an 

 egg ; its taste becomes acid, it exhales the odour of putrid fish, 

 and its surface is covered with abundance of the Byssus septica. 



When dried semen is exposed to heat in a crucible, it melts, 

 acquires a brown colour, and exhales a yellow fume having the 

 odour of burnt horn. When the heat is raised the matter swells, 



* Vauquelin, Ann. de Chim. ix. 71. 



