Scientific Intelligence. Anatomy and Physiology. 303 



observations, very much resembles in structure that of the bones ; 

 it has the same small cavities, and undulating canals, but it ap- 

 pears to have no bloodvessels, or cylindrical tubes, or radiated 

 canals. 



19- Microscopic Researches on the Structure of the Teeth^ 

 by M. F. Ditjardin. The author having detailed the recent 

 labours of Messrs Purkinje and Retzius (as stated above) re- 

 marks that Malpighi had, as early as 1667, observed the struc- 

 ture of the enamel, and that Leuwenhoeck in 1687 announced 

 that the bony portion is composed of a union of small tubes in 

 which he could perceive infiltrations, the result of capillary at- 

 traction. M. Dujardin then points out his method of obser- 

 vation, which consists in removing, by means of the small chissel 

 of the engraver, laminae of extreme fineness, either parallel to 

 the exterior surface, or in the direction of the natural fissures, 

 or perpendicular to the axis. The laminae thus procured with- 

 out roughness, which, be it observed, is not a little difficult, are 

 exposed under water, placed between two fine plates of polished 

 glass, and introduced into the microscope, varying the mode of 

 illumination, and augmenting the power of the light by means 

 of lenses placed underneath. The parallel laminae of the sur- 

 face exhibit in all teeth of mammalia, holes or pores of from 

 T1 1 C5 to j/so part of a line in size, and spaces j^ of a line, 

 so that there are from 380 to 500 in the length of a line. This 

 is nearly the number indicated by Leuwenhoeck, but the ob- 

 servations of Mr Purkinje differ, inasmuch as this observer has 

 found intervals five or six times as great as the pores or tubes. 

 These pores are sometimes round or oval, but they are irregular, 

 and elongated, and even appear to arise from the unity of se- 

 veral pores. This irregularity alone is sufficient to indicate 

 that they are not the orifices of tubes or vessels ; and besides 

 it is impossible to recognise in the fine laminae any difference 

 of density, forming a concentric circle round the pores, which 

 would have been the case if they were the sections of tubes or 

 vessels ; and moreover the rupture of these laminae does not 

 exhibit that they have proper parietes, which are more resist- 

 ing. The pores especially in the long teeth, such as the ca- 

 nine, assume a somewhat regular disposition in a longitudi- 

 nal direction, and it is in this direction also that the fissures 



