The distribution of ganglionic cells in the central area of the Beagle dog retina was studied by means of light microscopy in thirteen whole-mount preparations stained with cresyl violet. The central area was composed of two parts termed "the round central area" and the 'horizontal streak"; in some specimens thc former and in other the latter part was more prominent. The highest concentration of ganglionic cells occured in the round central area (about 7.100 cells/mm2). In other regions of the central area the cells were less numerous and the fewest number was found outside the central area. The size categories of ganglionic cells in the Beagle retina are comparable with those observed in other species.ti. 5.

Groups of 90 male broilers each were administered the antibiotic avoparcine mixed into feed in concentrations of 7.5, 10, and 15 ppm and achieved a higher mean body weight than the controls fed without this admixture. At the end of the 70-d fattening period, histological examination was carried out on selected individuals. The small intestine, liver, bursa of Fabricius, thymus, thyroid gland, pancreas, kidneys, heart, and skeletal muscle were observed on paraffin sections stained with hematoxylin and eosin. Cell proliferation was assessed in the liver and small intestine by means of bromodeoxyuridine labeling. The exposure to avoparcine resulted in a decreased cell proliferation in both tissues when compared to controls. In addition, hypertrophy of the hepatocytes and development of reactive lymphoid tissue in the bursa of Fabricius, which occurred in the controls, were absent in the treated animals. These observations indicate that the growth-promoting effect of avoparcine is related to a restriction in the host animals of responses to intestinal bacteria. No adverse pathological changes were observed in the examined tissues, indicating that avoparcine was well tolerated.

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The composition of both optic fascicles of a Beagle dog was studied in topographically oriented, semithin transections of whole nerve stained with toluidine blue. About 165,000 myelinated fibers were present in each nerve, their maximum caliber reaching 11 micron; large, less densely arranged fibers occurred especially in the dorso-temporal region.

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