52 The Microscope. 



CHAPTER VI. 



HA IKS AND FEATHEES. 



[HE scales of fishes, as Dr. Carpenter tells us, 

 are developed in the substance of the true 

 skin; whereas the scales of reptiles, the 

 feathers of birds, and the hairs of quadrupeds are 

 formed upon its surface, and allied in structure to the 

 epidermis or scarf-skin. They are essentially com- 

 posed of collections of cells, and form examples of 

 innumerable structures in which cellular formation 

 may be observed. In fact the microscope reveals to 

 us that all animal and vegetable structures are de- 

 veloped from cells, and the reader will find a lucid 

 and interesting account of their formation and changes 

 in " Hogg on the Microscope," p. 527, etc. 



Hairs and feathers are formed and developed on 

 the same plan essentially. They both grow from a 

 root, by continual additions of cells to the lower parts, 

 which cells become elongated, and push the hair or 

 feather farther and farther upward; and thus it 

 lengthens. When we pull a hair up " by the root," 

 we see a little bulb, which is filled with soft pulpy 

 cells, and this bulb corresponds to the quill of a 

 feather, also containing a soft pulp while grow- 



