Alkaline phosphatase is generally known to exist widely distributed in the vital body and is concerned with the synthesis and decomposition of phosphate compounds that play an important role in the metabolism. Activity of this enzyme is said to be particularly strong in the tissues active in their metabolism. ROBISON et al. [1] had earlier given their findings on the relation between alkaline phosphatase and dental calcification and ever since, studies dealing with alkaline phosphatase in dental pulp have been conducted with a view to throwing light on the calcifying mechanism of teeth.
Biochemical study on this alkaline phosphatase in dental pulp began with YAGIU [2] and OGAWA [3], MOTOMURA [4], SAITO et al. [5], MISEI et al. [6] and KANNO et al. [7] have been researchers in his wake. Among them, KIMIZUKA [8] purified alkaline phosphatase in dental pulp of rabbits through the specific activity and gave report on its enzymological properties. Localization of this enzyme has been histochemically attested to by many workers in the field and published research findings are numerous [9-29]. Although the method of histochemical evidence has advantageous features, there exists a danger of human elements creeping in through the inactivation of enzyme at a fixed procedure, diffusion or resorption of intermediate products in the staining process. Also we must be constantly on our guard against its distribution and detection peculiarities, as the result of histochemistry is only semi-quantitative. Therefore, any set of data needs to be very carefully handled for the analytical purpose. The present study is concerned with a method devised by the authors which is capable of measuring alkaline phosphatase activity in a sample of minute quantity. With this method, they examined the distribution of alkaline phosphatase in the dental pulp in terms of histoand biochemical light.

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From Hyracotherium of Europe, the oldest of the Equidae, parabunodont, with archaic molars, III (2) /II (2) (3 longitudinal rows of 2 tubercles, at the upper molars, 2longitudinal rows of 2 tubercles, at the lower ones), start off three chief phyla, every one extinct during the Tertiary era.
However, the actual Hyrax, by its jugal teeth, comes nearer to one of those phyla, the Palaeotherium's, of which, in the upper molars, the intermediate tubercles become effaced, while two transversal ridges, indicated, mark the toechodont type, as also do the. tubercles in V, at the lower molars.
The Equinae's phylum, of which the terminal genus, the horse (Equus), is still living, seems to separate, at the Miocene period, from a primitive north American off-spring.-At the upper molars, the intermediate crescent-like tubercles grow as big or bigger as the external ones, also in crescent, while the internal tubercles are diminishing.-The externalcrescent-liketuberclesofthelowermolars, asthefourmainonesoftheupper molars, grow more and more longer, in the antero-posterior sense, till Equus, still actual, where the belodont type attains its apogee.
By the molars' morphology (as, moreover, the extremities' morphology), Hyrax (Procaviidae) is revealed a relatively archaic perissodactyl, when the horse (Equidae), on the counter, is a very evoluted perissodactyl.

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