5 



BIOLOGICAL CHANGES IN THE SPLEEN OF 



THE FROG. 



ALICE LEONARD GAULE. 



Whoever has had occasion to experiment with frogs to any 

 extent has doubtless been often interrupted in the progress of 

 his investigations by the different behavior of the organs and 

 tissues at various seasons of the year. A number of Gaule's 

 pupils in the Physiological Laboratory at Zurich have made 

 these changes, directly or indirectly, the subject of investiga- 

 tion. Some of the results have already been published by 

 Ploetzi and by Leonard,^ others have merely been referred 

 to in the publications of Gaule,^ of Gurber,* and of Johannsen " 

 and others still await completion. The present investi- 

 gation has to do with the effect of the different seasons, 

 or of the natural external conditions on the spleen of the 

 frog. 



Habits of the Frog. 



The two common Swiss species are the green frog, Rana 

 escidenta and the brown or grass frog, Rana temporaria. The 

 life-habits of the two species fall into two annual periods, 

 (i) the period of hunger and (2) the period of nutrition. The 

 former extends over the winter and spring months, that is, 

 from November until the late spring when the nutritive period 

 begins. In November when the days become dark and cold 



1 Ploetz, Die Vorgange in den Froschhoden unter dem Einfluss der Jahreszeit. 

 Archiv £. Anat. u. Phys. Supplement Band, 1890. 



2 Leonard, Der Einfluss der Jahreszeit auf die Leberzellen von Ratta tempo- 

 raria. Archiv f. Anat. u. Phys. 1887, Supplement Band. 



3 Gaule, Zahl und Vertheilung der markhaftigen Fasern im Froschruckenmark. 

 Konigl. sachs. Gesell. der. Wissenschaften, Band XV, 1889. 



* Giirber, Die Gesammtzahl der Beutkorperchen und ihre Variation. Archiv 



fur Anat. u. Phys., 1889. 



5 Johannsen, Ringbander der Nervenfaser. Archiv fur Anat. u. Phys., 1892. 



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