116 LECTURE IV. 



the tooth (dentine) with its system of tubes, which ex- 

 tend nearly up to the surface, and in the root of the 

 tooth are directly continuous with a layer of real bony 

 substance (cement) the corpuscles of which are seated 

 upon the ends of the tubes. A provision for the con- 

 veyance of the juices similar to that which in bone ori- 

 ginates in the marrow, here takes its rise in the pulp, 

 whence the nutritive fluid can be conveyed up to the 

 surface by the means of tubes. 



These systems of tubes which are found in such a very 

 marked form in bone and the teeth, are to be seen with 

 far less distinctness in the soft structures, and it is chiefly 

 for this reason. I imagine, that the analogy which exists 

 between the soft connective tissues and the hard texture 

 of bone has r.ot been clearly comprehended. These sys- 

 tems are most distinctly seen in parts which are more of a 

 cartilaginous nature, as, for example, in fibro-cartilage. 

 But it is a fact of great significance that we find a series 

 of transitional forms between cartilage and the other 

 connective tissues, in which the same conditions are con- 

 stantly repeated. In the first place, parts which chemi- 

 cally belong to the class of cartilages, for example, the 

 cornea, which yields chondrine when boiled, although 

 nobody regards it as real cartilage. But more striking 

 is the arrangement in those parts in which the external 

 appearance speaks in favour of a cartilaginous nature, 

 but the chemical properties do not correspond, as for 

 example, in the semi-lunar cartilages (Bandscheiben) of 

 the knee-joint, which are interposed between the femur 

 and tibia for the purpose of protecting the articular 

 cartilages from too violent contact. These parts, which 

 even now are generally described as cartilage, yield no 

 chondrine on boiling, but gelatine ; and yet, in this hard 

 connective tissue, we meet with the same system of anas- 

 tomosing corpuscles that prevails in the cornea and in 



