180 SUiMMAKY OF CURRENT RESEARCHES RELATING TO 



much smaller diameter, thickness of com pacta, size of trabecular, and 

 greatly reduced weight of bones which were experimentally deprived of 

 the influence of mechanical stress and strain. The growth in diameter 

 is particularly affected. 



Development of Liver in Ground Squirrel.''" — C. E. Johnson has 

 studied the development of the liver in two species, Citdlus tridecem- 

 lineatus and C. franJcUni, and finds that it does not differ essentially 

 from that observed in other mammals. The earliest primordium is a 

 ventral thickening of the gut ; it becomes an outpouching of the wall ; 

 it shows three lobe-like divisions ; it becomes spindle-shaped and smooth- 

 walled ; trabeculse make their appearance ; to the primary hepatic 

 diverticulum or pars hepatica there is added the pars cystica, which arises 

 as an evagination of the gut wall, occupying the angle between the 

 pars hepatica and the yolk stalk ; this pars cystica is not a separate area 

 so much as a caudal extension of that thickened part of the tube which 

 has already given rise to the pars hepatica. The development of the 

 ducts is described. 



Development of Serous Glands of Tongue.j — E. A. Baumgartner 

 finds that serous glands first appear in the 8 • 5 human foetus as out- 

 growths of the vallate papilla of the tongue, usually from the lower 

 border, sometimes from the outer wall. The first outgrowth is knob- 

 like. Soon a stalk develops giving rise to lateral branches with enlarged 

 end-pieces. In a 19 cm. foetus these enlargements present bulgings of 

 the surface and beginnings of alveoli. In the newborn the serous gland 

 is alveolar, with some anastomoses between the alveoli. In the adult 

 some of the glands are tubular, with some anastomoses. In the new- 

 born, many knob-like outgro\\ths appear on the large ducts, probably 

 primordia or potential primordia of future glands. Cystic dilatations 

 of the serous ducts may occur. Mucous end-pieces occasionally open 

 into the ducts of the serous glands of ihe vallate papilla. Maziarski 

 referred the serous glands of the vallate papilla of man to the branched 

 tubular type. They belong to the branching tubulo-alveolar type. 



Angioblasts and Blood-vessels. | — Florence R. Sabin has studied 

 in chick embryo the differentiation of angioblasts from the mesoderm. 

 They are vaso-formative cells, more granular and more refractile than 

 the mesoderm cells ; their daughter-cells form dense syncytial masses, 

 Blood-vessels arise within the bodies of angioblasts, not between them. 

 The angioblasts produce blood-plasma, endothelium, and red blood-cells. 

 Red blood-cells arise from the endothelial lining of blood-vessels, and 

 also from angioblasts directly. 



Interstitial Cells in Reproductive Organs of Chicken. §— Alice M. 

 Boring and Raymond Pearl discuss the conflicting results : interstitial 

 cells are reported present and absent for male birds of practically every 



* Anat. Record, xiii. (1917) pp. 169-75 (4 figs.). 



t Journ. Amer. Anat., xxii. (1917) pp. 365-83 (3 pis.). 



X Anat. Record, xiii. (1917) pp. 199-204. 



§ Anat. Record, xiii. (l917) pp. 253-68 (6 figs.). 



