ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 169 



namber of alveoli contained in one air-sac is estimated to be from one to 

 twenty, eleven in average. The alveolar walls, other than the' base, are 

 formed usually by both the protruding wall of the alveolar ducts and the 

 alveolar septa. . J. A. T. 



Histology of Vertebrate Lung. — Ch. Ogawa {Amer. Journ. Anat., 

 l'.)20, 27,> 833-93, 28 figs.). A comparative study in Amphibians, 

 Reptiles, Birds and Mammals of the respiratory epithelium, the muscle 

 fibres, the elastic fibres, and the reticular fibres. The respiratory 

 epithelium of reptiles is intermediate between that of amphibians and 

 that of mammals. It seems to be absent in birds, mole and bat. The 

 muscle fibres are entirely absent in all parts of the alveolar ducts in the 

 bat lung, and they are usually absent from the alveolar walls. The 

 distribution of the elastic and the reticular fibres is described in detail, 

 but we cannot do more than indicate the general nature of the investi- 

 gation. J. A. T. 



Paranucleus of Pancreatic Cells. —P. Pt. Chaves {Gomptef^ Rendiis 

 Soc. BioL, 1920, 83, 8S1-4). Methods of technique may cause sudden 

 coagulations and the like in the cytoplasm, and some of the resulting 

 lamellar or fibrillar products have been called Nebenkerue or paranuclei. 

 Others are due to nucleoli which migrate into the cytoplasm. These 

 usually show a central and a peripheral substance, differing in their 

 reactions. The precise mode of expulsion and migration of the nucleoli 

 is ol;)Scure. They begin to exfoliate into a number of lamellae, and 

 probably dissolve"^ in the cytoplasm. Thus, besides the lamellar para- 

 nuclei arising as artefacts from the condensation of ergastoplasmic 

 filaments, there are true paranuclei of nucleolar nature and origin. 



J. A. T. 



Transformations of Hepatic Cell in Hedgehog.— P. E. Chaves 

 (Conij)tes Rendus Soc. Biol, 1920, 83, 879-81). During embryonic life 

 the hepatic cell becomes vacuolated, increases in size, and accumulates 

 fat which subsequently disappears. The chondriosomes, at first very 

 small, are transformed into large rodlets and granulations. The vacuoles 

 become confluent and increase in size, forming a secretion which 

 disappears in the sucking young. After birth the transformations 

 continue, those of the chromosomes being remarkable. During the 

 lactation the fat reappears. J. A. T. 



Giant-Cells of Bone-Marrow. — H. E. Jordan {Amer. Journ. Anat., 

 1920, 27, 287-313, 27 figs.). The red bone-marrow of the rabbit and 

 the guinea-pig contains three chief varieties of giant-cells : (a) Mega- 

 karyocytes, the mononucleated forms derived by excessive growth from 

 the ha^moblast ; (Jf) polymorphokaryocytes, the forms with polymor- 

 phous or lobulated nucleus derived from the megakaryocyte by incomplete 

 direct division of the nucleus ; and (c) polykaryocytes, the multinucleated 

 forms derived from forms with lobulated nuclei by completion of the 

 constrictions in the complex nucleus to produce separate smaller and 

 -spheroidal nuclei. Certain giant-cells of the multinucleated variety, 

 chiefly hi- or quadri-nucleated, retain to the small degree the power of 

 producing ultra-cellular erythrocytes. The giant-cells in normal marrow 



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