PHYSIOLOGICAL STUDIES OF GUSTATORY MECHANISMS 



245 



been completed. Preliminary observations indicate that the majority of 

 individual fasciculi contain approximately the same percentage of fibers in 

 each fiber diameter group. Some striking variations to this pattern have 



2 4 6 8 10 12 14 16 18 20 



HORSE 



CAT 



Fig. 10. Superimposed histograms of myelinated fiber diameter distributions 

 of the chorda tympani nerves of the cat and the horse. Each histogram represents 

 the average number of fibers in three nerves. Observe the larger number of larger 

 diameter fibers in the horse. See also Table 1. (Engebretsen and Kitchell, 



unpublished). 



been seen. Some fasciculi contain proportionally large numbers of small 

 fibers and others have substantially larger numbers of large fibers (Fig. 6). 



Some of the chorda tympani nerves were prepared, sectioned, and stained 

 using the Holmes silver technique (Holmes, 1947). Quantitative studies of 

 these preparations have not been completed. The number of unmyelinated 

 fibers varies considerably. In Fig. 8 it can be seen that one fasciculus has 

 fewer myelinated fibers in an area than are found in a comparable area in 

 another fasciculus. This fasciculus contains large numbers of unmyelinated 

 fibers. The significance of these variations is unknown. 



Previous studies of the chorda tympani nerve in animals are incomplete 

 in respect to fiber diameter distribution. Only the total number of mye- 

 linated and unmyelinated fibers has been estimated using various silver 

 staining methods and sampling counting techniques. Foley (1945) esti- 

 mated that there was an average of 1591 myelinated fibers in the chorda 

 tympani nerve in cats and 2760 myelinated fibers in the chorda tympani 

 nerve in dogs. These estimates are in general agreement with our direct 



