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dodson on rabbits.

big ass rodent skull (capybara) on display. we may have g pigs as well as 
rabbits, or not have rabbits, or g pigs at all. we'll see. rabbits are 
NOT rodents of course. they are lagomorphs. rabbit and g pig dissection 
is listed in smallwood in the lab animal section.

capybara- semi aquatic kinda like a pygmy hippopotomus, south american, 
about 100 lbs.

why aren't rabbits rodents?

there are two orders....lagomorpha and rodentia....

lagomorphs: rabbits, hares, pikas. pikas are small guys up in the rockies 
at high altitude, look kinda like small marmot or groundhog with large 
ears.

rodents are rats, mice, g pigs, etc etc etc. dr d says there are probably 
some among us right now in this room

similarities between the orders: both chewing/gnawing animals with 
continuously growing incisors. this growth can cause problems in case of 
malocclusion, etc, teeth can grow the wrong way, or they can overgrow, 
etc.

also high reproductive capacity, short gestation, large litters. they're 
like animal weeds....or something.

there are about 50 species of lagomorphs, about 1600 species of rodents.

when jesus said "the meek shall inherit the earth" he may have had 
rodents and cockroaches in mind. - Dr. Dodson.

rodents are physiologically very hardy. good at stowing away on ships, 
floating debris, etc. rabbits don't seem to do that.

rodents can pronate and supinate their forelimbs, rabbits can't.
not ALL rodents can, though.

like horses, rabbits are developed more for speed, so they can't pronate 
and supinate.

rodent skull is basically ramrod straight, while w/rabbits, the skull has 
a sharp flexion - like a goat. in rabbits, the axis of the face is at an 
angle to the axis of the brain case; not so in rodents.

teeth: rabbits and rodents have many transverse rows making a grinding 
surface.
the rodent has an elaboration of the masseter muscle - in south american 
rodents including capybara, g pigs, etc, part of the masseter comes off 
cheekbone per normal, and part comes out of a hole beneath the eye and 
comes all the way forward to the nose. skull of porcupine, also a s. 
american rodent, also has this hole. in n. american rodents, eg beaver, 
instead of perforating the zygomatic arch, the masseter comes way far 
forward on the outside of the arch. many but not all rodents have cheek 
teeth that grow continuously.

rabbits also have a double row of incisors.

anatomy of rabbits

first examine external features of rabbit. both sexes have inguinal 
sinuses - in male, between the penis and the scrotum, may have a waxy 
secretion there.

rabbits are long bodied, w/ 7 lumbar vertebrae. they are powerful runners 
with very strong hind legs. clinically they are prone to back injury. 
lumbar fracture is exceedingly common in improperly handled pet rabbits 
and px is poor.

male rabbits have wide open inguinal canals. the testes can be withdrawn 
voluntarily - so they can be abdominal or descended at any particular 
time.

rabbs have a simple stomach. many rodents have a prominent nonglandular 
part of the stomach, but in rabbits they have a simple stomach w/no 
nonglandular part.

jejunum is long. well developed ileocecal fold in rabbits.

rodents kind of more like horses/ruminants than dogs cats.

before the ileum joins the cecum is a dilation called a sacculus rotundus 
and the ileum is pale colored with much lymphoid tissue in the wall.  
cecum kinda horselike...wide, sacculated. it's spiraled/wound up rather 
than laid out straight. it ends in a long prominent vermiform appendix. 
adjacent to sacculus rotundus where colon begins there is another ampulla 
at the base of the colon. this is called the ampulla of the colon and 
when the colon starts out, it's horselike, sacculated. descending colon 
not truly sacculated.

rabbits/rodents both are reingesters of feces. they produce soft and hard 
feces, and the soft feces are reingested. they're "proctal feeders" or 
"coprophages" or "fecal feeders" these are cecal pellets.

prostate not big. bulbourethral glands, vesicular glands, big.

they have a duplex type uterus - with a median septum dividing it. a 
simplex cervix.

g pig dig tract simple stomach, prominant cecum, ascending colon has 
spiral loop like ruminants, a bit simpler. descending colon ...

male g pigs have huge vesicular glands, 10 cm long, weird appearance. 
kind of antlerlike. the prostates are prominent, there are accessory 
glands called "coagulating glands" which help form a copulatory plug, so 
after the sex act a plug forms in vagina to discourage entry of sperm 
from another male.

one other thing about rodents/rabbits. these are claviculate mammals, 
they do possess a clavicle.

claviculate mammals: rodentia, lagomorphia, primata, bats, insectivora




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