144 PROGRESS OF MICROSCOPICAL SCIENCE. 



permanent ossifications of the mandible are all membrane bones in 

 Fish, Frog, and Fowl ; but in tlie Mammal (exceptionally) the ramus 

 has a cartilaginous foundation. The hyoidean becomes closely united 

 with the mandibular arch, and then segmented, in the Fish, into the 

 hyo-mandibular, the stylo-hyal, cerato-hyal, and hypohyal — the hyo- 

 mandibular, or proximal segment, articulating with the outer wall of 

 the periotic, and many of the segments of the arch becoming dis- 

 located. 



In the Frog the hyoid also becomes segmented, but only after 

 extensive coalescence with the mandibular arch. The proximal seg- 

 ment becomes the suprastapedial (hyo-mandibular) with its extrasta- 

 pedial process, and, extending inwards as mediostapedial and inter- 

 stapedial, articulates with the stapes, developed by segmentation from 

 the outer wall of the auditory capsule. The stylo-hyal is dislocated, 

 and becomes connected with the auditory capsule below the stapes 

 (opisthotic region). 



In the Bird the hyoidean arch remains distinct from the mandi- 

 bular. Whilst in its primordial condition it coalesces by its incurved 

 apex with the auditory capsule in front of the promontory, before the 

 stapedial plug is segmented. It then chondrifies as three distinct 

 cartilages — an incudal, a stylo-hyal, and, distally, a cerato-hyal. The 

 stapes becomes free from the auditory cajjsule, but remains united with 

 the cartilaginous part of the incus (mediostapedial) ; the ascending 

 part is largely fibrous (suprastapedial), and the j^art loosely attached 

 to the mandibular arch is the elongated extrastapedial. The short 

 stylo-hyal afterwards coalesces with the body of the upper or incudal 

 segment by an aftergrowth of cartilage (the interhyal tract) ; a long 

 membranous space intervenes between it and the glossal piece (cerato- 

 hyal). Thus the " columella " of the Bird is formed of one periotic 

 and three hyoidean segments. 



In the Pig the hyoidean arch is distinct, but articulates closely 

 with the mandibular ; its upper segment (hyo-mandibular) is con- 

 verted into the incus, and becomes connected with the stajjes. The 

 stylo-hyal is dislocated, and coalesces with the opisthotic region of 

 the auditory capsule. 



Betrograde Changes in the Neiv Formation of Blood-vessels in Bone 

 and Cartilage. — In the ' Medicin Jahrbiicher' (vol. iv., 1873) Herr 

 Heitzman asserts, says Dr. E. Klein in the ' Medical Eecord ' (August 

 6th), that in long bones of young dogs the material contained in the 

 vascular canals is, up to the blood-vessels, gradually ti'ansformed into 

 bone-tissue. The blood-vessel itself, after having changed into a solid' 

 jn-otoplasmic cone, finally also gives origin to bone-cells and bone 

 ground -substance. In bones artificially inflamed, an abundant forma- 

 tion of new vessels of a cajiillary character takes place from the ele- 

 ments of the decalcified tissue as well as from those lying in the 

 absorption cavities, viz. derived from bone-cells. The former Heitz- 

 man observed in a scapula of a cat in the third day of inflammation, 

 produced by injuring its posterior margin with a forcejis ; the latter 

 in that of a dog in the fourth day of inflammation, produced by per- 

 forating its centre. In both instances Heitzman was able to follow 



