86 



GENERAL ANATOMY. 



exception), on the lining membranes of the bloodvessels, on many of the mucous 

 membranes, and in the ducts. The nails, hairs, and in animals the horns, are 

 a variety of this kind of epithelium. 



The columnar epithelium (Fig. 44) is formed of cylindrical or rod-shaped cells, 

 each containing a nucleus, and set together, so as to form a complete membrane. 



This form of epithelium covers the mucous membrane of the whole gastro- 

 intestinal tract and the glands of that part, the greater part of the urethra, the 

 vas deferens, 'the prostate, Cowper's glands, Bartholine's glands, and a portion 

 of the uterine mucous membrane. 



The spheroidal or glandular epithelium (Fig. 45) is composed of circular cells, 

 with granular contents and a small nucleus. 



This form is found in the kidney, ureters, and bladder, and in the secreting 

 glands. 



Ciliated epithelium (Fig. 46) may be of any of the preceding forms, but usually 

 inclines to the columnar shape. It is distinguished by the presence of minute 



Fig. 46. 



[Fig. 47. 



Simple conoidal ciliated epithelium, a. Nucleated cells. 

 b. Cilia and their free extremities.] 



processes, like hairs or eyelashes (cilia), 

 standing up from the free surface (Fig. 47). 

 If the cells be examined during life, or imme- 

 diately on removal from the living body (for 

 which in the human subject the removal of a 

 nasal polypus offers a frequent opportunity), 

 in tepid water, the cilia will be seen in active 

 lashing motion, and if the cells be separate, 

 they will often be moved about in the field 

 by that motion. 



The situations in which ciliated epithelium is found in the human body are: 

 the respiratory tract from the nose downwards, the tympanum and Eustachian 

 tube, the Fallopian tube and upper portion of the uterus, and the ventricles of 

 the brain. 



Ciliated epithelium, from the liuruau tra- 

 chea. (Magnified 350 times.) a. Innermost 

 layers of the elastic longitudinal fibres, b. 

 Homogeneous innermost layers of the mu- 

 cous membrane, c. Deepest round cells, d. 

 Middle, elongated, e. Supeifisial, bearing 

 cilia. 



SEROUS, SYNOVIAL, AND MUCOUS MEMBRANES. 



These membranes consist of a layer of epithelium supported on a structure- 

 less membrane, called the basement membrane, beneath which lies a tract of 

 connective or areolar tissue, which in the mucous membranes lodges glands of 

 various kinds, and contains unstriped muscle, or contractile muscular iibre- 

 cells, and in both serous and mucous membranes conveys the bloodvessels out 

 of whii-h tin; secretion is to be eliminated. 



The Serous Membranes are the simplest of the three, and will therefore be 

 first described. 



They form shut sacs, sometimes arranged quite simply, as the tunica vaginalis 

 testis, at others with numerous involutions and recesses, as the peritoneum, but 

 which can always be traced continuously around the whole circumference. The 

 sac is completely closed, so that no communication exists between the serous 

 cavity and tho parts in its neighborhood. An apparent exception exists in the 

 peritoneum of the female; for the Fallopian tube opens freely into the perito- 

 neal cavity in the dead subject, so that a bristle can be passed from the one into 



