AQUEOUS SECBET10NS. lit 



Dr. B. And yet it is no easier to explain it on any 

 chemical principles, with which we are acquainted, than 

 the other functions of life. They all indeed are govern- 

 ed by laws apparently chemical, and to such a degree as 

 to justify the language of a very distinguished French 

 physician, who has styled them a " vital chemistry." Of 

 the precise manner in which this function is performed 

 we are totally ignorant. 



Emily. But what is the nature of the secretory or- 

 gans ? Cannot we obtain some light from this source ? 



Dr. B. Not the least. We here feel the full force 

 of a truth recognized by anatomists, that the most per- 

 fect knowledge of the structure of a part does not nec- 

 essarily lead us to a knowledge of its function. The or- 

 gans of secretion are so varied in their form and struc- 

 ture, that it is difficult to exhibit a correct general view 

 of them, and an idea of their details can be obtained on- 

 ly by personal examination. They are called glands ; 

 they vary in size from that of a pin's head to the magni- 

 tude of the largest organs in the body and are generally 

 of a rounded shape. They consist of a multitude of mi- 

 nute arteries and veins connected by means of cellular 

 substance. The fluid which is secreted from the blood 

 in these vessels, is either taken up and carried away to 

 fulfil its destined purpose, by other vessels, or more 

 properly ducts ; or the fluid is poured out directly as fast 

 as it is secreted, on the surface of the parts where the 

 glands are placed, without the intervention of any duct. 

 To obtain a clearer jdea of the secretions, we will dis- 

 tinguish them into the five following classes, viz : the 

 aqueous, the serous, the mucous, the oleaginous, and the 

 resinous , 



Emily. -And all these are derived from one and the 

 same source the blood. What an immense storehouse 

 of heterogeneous materials, this fluid must be ! 



Dr. B. We have not time to say much about them, 

 and therefore, shall barely say enough to give you some 

 idea of their nature and use. The aqueous consists al- 



