22 



CKOliClO L, STIlEF/nOll 



iziiifi; through it arc Mic loops of small blood vessels. The pcri- 

 choiulriuiu forms in tiu' outer part of this reticuhim as a compact 

 fibrous uieiubrano. l\^rii)luvral to the ])('rich()n(lrium tlio tissue 

 is still of a roticuUir ty]io but passes hi rapid transition hito pre- 

 cartilage and then into a, tiiie cartilaginous tissue. 



After making its first a|)i)eai'ance, the ix'richondrium ra])idly 

 becomes more consi)icuous. In fetuses 80 mm. CU length (Car- 







enchonciriur 



V\\l,. II l'li(it(ifir;i|)li (if seel ion lliiou^li I lie posi ciior scinicircul;! r cm nal in a 

 liunian fclus 7.'{ imn. loii^ (C'aincfiic ( 'olloction, No. 1873). JMilarficd 100 di- 

 ameters. It siuiws I lie pcticlioiKlriiiiii in its cai'liest form. 



negie Collection, No. 172) it consists of a dense hbrous coat more 

 than twice as thick as that shown in Hgiu'e 12. It is clearly 

 separated trom the cartilage by a narrow zone of transitional 

 precartihige-i"(>ticular tissu(\ In slightly older fetuses, S5 nun. 

 CH length, (CaTn(>gi(> ( \)ll(H'tion, No. 14()()-3()) it has become a 

 (Umisc broad zone sei)arat(Hl from lh(> surroundhig cartilage only 

 by a, narrow cleft of transitional tissue which still, however, can 

 be recogniz(Hl as reticular in character. In fetuses 130 nun. CR 

 long (Carnegie Collection, No. 1018) the perichondrium presents 



