334 HUMAN UTERUS AND FCETAL APPENDAGES. 



the villus. It consists of a network of protoplasmic threads, which start from 

 nucleated masses. There are many large meshes, which are partly occupied by 

 the very large, coarsely granular, wandering cells, /, /. The wandering cells 

 generally are widely scattered, but sometimes are present in large numbers. 

 They are usually interpreted as foetal leucocytes. They differ, however, by 

 their large size and appearance strikingly from the leucocytes of the adult. We 

 have no knowledge of their history or functions. About the capillary blood- 

 vessels, v, the network is more finely spun. Around the larger blood-vessels the 

 mesoderm has a distinct intercellular substance with a tendency to fibrillar 

 differentiation in quite a wide zone around the blood-vessels. In this zone the 

 cells become elongated or irregularly fusiform. Around the larger vessels the 



vr r 



Fig. 193. — Adenoid Tissue from a Villus of a Human Placenta of Four Months. 

 /, /, /, Wandering cells, v, V, Capillary blood-vessels. J, Finer meshwork surrounding a capillary. X 35 2 diams. 



cells are grouped in laminae, and apparently are contractile, so that they must be 

 looked upon as an imperfectly differentiated form of smooth muscular tissue. 



Decidua Serotina at Seven Months. 



Specimens may be treated as described for the placenta in situ (page 329). 

 If, however, the best results are desired, the whole of the uterus should be cut 

 through and the placenta divided into smaller pieces from 1 to 2 cm. in diameter, 

 so as to allow a freer penetration of the preserving fluid. Either Zenker's or 

 Tellyesnicky's fluid is recommended. In a normal uterus about seven months 

 pregnant we find the following relations: The serotina is about 1.5 mm. thick, 

 and contains an enormous number of decidual cells (Fig. 194); the cavernous, 



