140 BACTERIOLOGY 



Observation of Infected Animals. — In nearly every case it will 

 be well to keep a record of weight of the animal from time to time. 

 The temperature may be observed by means of a thermometer 

 in the rectum. It should be inserted a considerable distance, 

 4 to 8 centimeters in guinea-pigs. Other examinations are made in 

 special cases, such as palpation of the lymph glands in tubercu- 

 losis and microscopic examination of the blood in anthrax, tryp- 

 anosomiasis and the relapsing spirochetoses. 



Post-Mortem Examination of experimental animals is often 

 of great importance. The body is first soaked in bichloride solu- 

 tion 'to wet thoroughly the hair and skin. It is then fixed on a 

 board by cords or by nails through the feet, stretched out with 

 the ventral surface exposed. With sterile scissors an incision 

 is carried through the skin in the median line from neck to pubis 

 and branch incisions are carried to the extremities. The skin is 

 reflected with aid of a scalpel and the desired examinations of the 

 subcutaneous structures carried out. The abdominal muscle 

 layei: is then seared with a hot iron in the median line as are also 

 the lateral walls of the thorax and with a new set of sterile in- 

 struments the seared line is incised so as to expose completely 

 the contents of abdomen and thorax. Heart's blood is obtained 

 by searing the epicardium and pimcturing the right ventricle 

 with a sterile glass Pasteur pipette. Any or all the organs of 

 thorax and abdomen may then be removed to sterile glass dishes. 

 Immediate microscopic examination for microorganisms is made 

 by direct slide-coverglass preparations of the fresh material diluted 

 with sa.lt solution and by smearing the fluids and tissues on cover- 

 glasses or slides and staining them by various methods. Cultures 

 are also made and it is important to make plate cultures directly 

 from the animal in all instances "in which a mixed infection or 

 possible contamination with extraneous organisms is suspected. 

 To remove the spinal cord, the animal is turned so that the back 

 is exposed, the skin divided by a median incision and stripped 

 back to either side. The muscles are roughly dissected away from 

 either side of the spinal column and the vertebral laminae are 



