76 EXAMINATION OF ADULT CUTICLE. 



closely resembling that of cuticle, is softer and much 

 more easily investigated. 



At an early stage of development it is not possible 

 to distinguish the masses of bioplasm which are to 

 form the cuticle from those which take part in the 

 development of the true skin with its nerves and 

 vessels, glands, hair, and adipose tissue. And at the 

 deep part of the cuticle, even in old age, will in- 

 variably be found numerous naked masses of bioplasm, 

 which exactly resemble those present at a very early 

 period of development, 45. 



116. Examination of Adult Cuticle. Suppose 

 we examine carefully a portion of adult cuticle. The 

 oldest part of this structure is on the outside, arid 

 the youngest^ or that which has been most recently 

 formed, is situated nearest to the blood, whence the 

 elementary parts or cells draw their nutritive supply. 

 If we make a perpendicular section of this structure 

 and place it under the microscope, we shall find that 

 in different parts of it the " cells " present very 

 different characters. . The deep portion which is 

 nearest to the vessels consists of small masses of 

 bioplasm, surrounded only by a trace of very soft 

 formed material. These are situated very close to 

 one another. A little above this the masses have a 

 more definite arrangement, and each oval mass of 

 bioplasm, now grown larger, 117, is surrounded by 

 a thin layer of formed material like an external 

 membrane. Still nearer the surface the elementary 

 particles are seen to be larger, both bioplasm and 

 formed material having increased in quantity. As 

 we approach the free surface, the cells become more 

 or less flattened, and the bioplasm is much reduced 

 in proportion. The formed material is harder and 

 more condensed. Lastly, the oldest elementary parts 

 upon the surface, which are rubbed away in great 

 numbers, and possess no bioplasm whatever, seem to 

 be composed entirely of cuticular substance or formed 



