Comparative anatomy of the caudate nucleus in different mammals.

Volumetric comparisons of the caudate nucleus of different mammals including rat, rabbit, cat, zebra, deer, antelope, bull, horse, dolphin (Stenella graffmani) and human are presented. A linear regression coefficient is obtained with its corresponding correlation coefficient. The results indicate that there is not a close correlation between the size of the caudate nucleus and the brain weight of the different animals studied when the caudate of the horse is included. When it is omitted there is a close correspondence. The caudate nucleus of the horse is extremely large in relation to its brain weight. The possible meaning of this fact is discussed. Measurement of different brain structures is of interest, both from the purely descriptive aspect and because it can suggest phylogenetic relations as well as explanation of functional differences in different animal species (1, 2).