THE MICROSCOPE IN PATHOLOGY AND MEDICINE. 243 



10. Sarcina ventricuH, in the stomach. 



11. Epizoa, or animals living upon the skin and hair. 



1. Pediculus, or louse, three forms: P. corporis, P. capi- 

 tis, and P. pubis. 



2. Acarus scabiei, or itch insect. 



3. Demodex folliculorum, inhabiting sebaceous and hair- 

 follicles. 



III. Entozoa, or internal parasites. On page 171 we 

 have given a general account of the Entozoa. At least 

 thirty different forms have been described as infesting 

 the human body ; eight species of Tcenia and two of 

 Hothriocephali, genera of the family Cestoidea or tape- 

 worms, of which the Cysticerci and Echinococci (vesicu- 

 lar cysts containing^ an embryo head provided with a 

 circle of booklets, and giving rise to the appearance of 

 measly flesh in animals) are larval forms; nine species of 

 Trematoda, or fluke-like parasites, existing in an encysted 

 and a free state; and eleven species of Nematoid, or round- 

 worms, including the common round-worms or Ascaris, 

 the Trichina spiralis, and the Filaria oculi, etc. 



Students who have not access to Dr. Cobbold's great 

 work on parasites, may find an excellent resume in Dr. 

 Ait ken's Science and Practice of Medicine. 



VI. EXAMINATION OF SPUTA. 



The microscopic examination of sputa is important in 

 practical medicine, but requires familiarity with the ap- 

 pearance of different structures under different magnify- 

 ing powers, as fragments of food, muscular fibre, starch, 

 etc. 



We may usually expect to find mucus, entangling air- 

 bubbles, and pavement-epithelium from the mouth (Plate 

 XXVII, Fig. 204). In catarrhal affections, ciliated epi- 

 thelium from the nasal or respiratory passages may also 

 be seen, and perhaps molecules of fat, pus-globules, blood, 



