CHAPTER VIIl. 

 THE FROG (continued) : the microscopic examination 



OF the compound tissues — GLANDS — SECRETION AND 

 ABSORPTION. 



With the exception of the tissues of the nervous system, 

 which will be described later on (Chap. X)^ we have now 

 studied the principal simple tissues by the method of dis- 

 sociation, i.e. by separating their constituent parts. We have 

 now to consider the way in which these tissues are combined 

 in the various organs, and for this purpose must adopt some 

 method of examination by which they are seen in their 

 natural relations. 



The method adopted for this purpose is that of section 

 cutting. You know how, by cutting sections, in various 

 directions, of a bit of twig, the arrangement and natural 

 relations of its various parts — wood, bark, and pith — can be 

 ascertained. The same thing applies to the organs of the 

 frog and other animals, but owing to their soft and non- 

 resistant texture, it is impossible to cut them into sections 

 thin enough for microscopic examination without special 

 preparation. The methods employed are by no means easy 

 for the beginner, especially without verbal instruction and 

 the resources of a biological laboratory, but in the event of 

 your wishing to make the preparations described and 



