70 THE FROG 
E. The Skeleton.—The following preparations are desirable, 
the number of each depending on the size of the class: 
Complete articulated skeleton, with hyoid intact. 
Articulated skull. Disarticulated skull. 
Cartilaginous cranium, in alcohol. 
Pectoral girdle, in alcohol. Pelvic girdle. 
Vertebral column, strung on wire. 
Hand and foot, mounted on cardboard. 
Hyoid apparatus, in alcohol. 
Miscellaneous bones, disarticulated. 
Entire articulated skeletons require considerable time for their 
preparation; good ones may be obtained from dealers at reason- 
able prices. Articulated skeletons may be prepared from speci- 
mens hardened in formalin, provided they have not been pre- 
served too long in the formalin; but the bones must be cleaned by 
the tedious process of picking away the muscle piecemeal with 
forceps. Formalin specimens are undesirable for the prepara- 
tion of disarticulated skeletons, since it is difficult to make even 
tolerably clean preparations. 
Freshly-killed specimens are to be preferred when available, 
since the task of removing the muscles may then be simplified 
by boiling. Remove the skin from the frog, separate the fore- 
limbs together with the pectoral girdle, and boil the parts for a 
few minutes in water, or better, in soap solution prepared by heat- 
ing and thoroughly mixing the following: 
aT RSOAD woes cue es TD sto eteiene ori citesatta ss sues Misiueyenere Miokeier eve 75 grams 
Potassnumenitrate (Salipetetabeaniec\s< siciole cuslonoions euterelimiotereere I2 grams 
Strong ¢amimOm1 ay cers c.cuoroeteiers is fora ei-si< e)e ayn oreistecensws saetere s\stoie ene TEOMCCs 
DistilledwontsoLt water joecass cveys%e.s ciere evarteliersyekererieucis) she ae 2,000 C.c. 
For use, one part of this stock solution is diluted with three parts 
water. If an articulated skeleton is desired, care must be taken 
not to boil too long, as this will soften and weaken the ligaments. 
Pick and brush away as much of the flesh as possible, repeating 
the boiling if necessary. 
Complete articulated skeletons are best mounted in glass jars 
containing alcohol, since in dry preparations the delicate carti- 
laginous parts such as the hyoid apparatus and the suprascapulas 
become shriveled. If for any reason a dry preparation is desired, 
it may be mounted on a wooden base and covered with a rec- 
