I have purchased preserved biological specimens from both Carolina Biological Supply Company, a major corporation, and the smaller discount company Bio Corporation. Of the two, I recommend Carolina hands down, unless you are on a very thin budget. Carolina's specimens are more consistent and are much
fresher in the color and texture of the flesh. The specimens from the latter are uglier and more rubbery, and I have received a few fetal pigs from them which were filled inside with some kind of disgusting goop — a clotted soup of blood and preservative, if I had to guess — although not all of their pigs were this way. The preservative that Bio Corp uses for
dry specimens is so pungent that it causes pain if the vapors get in your eyes or nose.
Nevertheless, the specimens from Bio Corporation can be worked with, and are definitely much cheaper than those from Carolina. Furthermore, you can get some pretty remarkable things from them that aren't available elsewhere. For example, one of the most fun demonstrations I performed one year involved a sheep's head, sawn down the midline to reveal a
medial sagittal section.
This specimen provided what I thought was a beautiful cross-section of the brain, in situ. You can notice in the photograph both the cerebrum and the cerebellum. Notice also the proportions—the cerebellum is almost as large as the cerebrum, and the brain as a whole still occupies a small fraction of the space inside the head. A large part of the space inside a sheep's head is occupied by sinuses. In a human head, about half of the space is occupied by brain, and most of that is cerebrum. The cerebrum is proportionally much larger in a person than in a sheep.
So to summarize my experience: It might be a good idea to purchase specimens from a discount supplier like Bio Corp if you are on a tight budget, or if you are looking for certain specialized items, but otherwise, stick to a major, reputable company like Carolina.