GENERAL BIOLOGY 



cavity near the oesophagus. It has no connection with the ovary. 

 (3) The kidneys are elongated, red masses close to the vertebral 

 column ; on the ventral surface of each is an elongated yellowish 

 body the adrenal body. Entering the kidneys on their external side 

 are the renal-portal veins; leaving the kidneys on their mesial side 

 are the branches of the inferior vena cava. (4) Ureter, a whitish 

 duct on each side passing from the outer side of the kidney into 

 the cloaca. (In the male this serves also as a vas deferens.) (5) 

 The urinary bladder, a large bi-lobed sac ventral to the rectum (it 

 can be inflated through the cloaca by means of a blow-pipe). 

 Make a diagram of the urino-genital system of your specimen. 



5. THE NERVOUS SYSTEM. (Preserved Specimen.) 



a. DISSECTION. 



Finish the exposure of the brain and spinal cord. With strong 

 forceps pick off bit by bit the roof of the skull, and remove the 

 dorsal part of the vertebral arches in the same way. A delicate 

 pigmented membrane (pia mater) covers the brain and the spinal 

 cord but may be concealed in the latter region by soft substance 

 (coagulation products after death) that can be washed away with 

 a stream of water from a pipette. 



b. THE BRAIN. 



If this is not injured in exposing it, note : 



1. Rhinencephalon or anterior part made up of two olfa\ctory 

 lobes extending anteriorly from a common median part as two 

 cylindrical so-called olfactory nerves to branch inside the nasal 

 chambers. 



2. Prosencephalon or cerebrum composed of two large masses, 

 the cerebral hemispheres, separated by a median groove, 

 pheres. Upon it is a very small pineal gland and below this a cen- 



3. Diencephalon, a mass between and posterior to the hemis- 

 tral cavity, the third ventricle, bounded on the sides by masses 

 called optic thalami. 



4. Mesencephalon, showing on the dorsal side a pair of large, 

 rounded, hollow bodies, the optic lobes. 



5. Mentencephalon or cerebellum, a small mass extending 

 across the anterior edge of a large triangular cavity, the fourth 

 ventricle. 



6. Myelencephalon or medulla oblongata, forms the remainder 



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