New-Formation of Hemal Nodes. 



4i 



veins the prevertebral hemolymph nodes were very hyperplastic, 

 and the gastro-splen'c and great omentums were strewn with 

 small reddish points that microscopically present the appearance 

 of developing hemal nodes. In the dog killed two years after 

 the ligation very remarkable changes were found, the omentums. 

 mesentery and peritoneum in the upper left quadrant were strewn 

 with innumerable red nodes, varying in size from that of a pin- 

 head to that of a pea, and in two cases, as large as a cherry. These 

 large ones had all the gross appearances of accessory spleens; but 

 they had not been present at the time of the operation. Micro- 

 scopically these nodes presented all stages of transition in the 

 development of hemal nodes, from the minute dilated lobule of 

 sinusoidal capillaries in the fat tissue up to the fully developed 

 hemal node resembling an accessory spleen. These nodes were 

 precisely the same as those in the preceding case. In both cases 

 the spleen was atrophic. 



Conclusion. — Splenectomy in dogs is not comparable in its 

 effects upon the lymph nodes to the same operation in sheep and 

 goats. In only two out of twenty-four dogs was any hyperplasia 

 of the lymph nodes found, and no new-formation of hemolymph- 

 nodes or splenic tissues. 



Ligation of the splenic veins seems to produce much more 

 decided results after the lapse of one or two years following the 

 operation. Three out of eight dogs showed marked hyperplasia 

 of the prevertebral nodes, and the two cases examined after longest 

 intervals showed a new-formation of hemal nodes in the splenic 

 region, the largest newly formed nodes resembling accessory 

 spleens. These structures were not present at the time of the 

 operation. 



They are not inflammatory in character. 



Individual dogs must have different capacities for hyperplasia 

 and regeneration. The minute capillary plexuses from which 

 these nodes arise may represent preformed accessory spleen anlage. 



Tizzoni's statements are hereby confirmed and Meyer's objec- 

 tions negatived. 



