LESSON X 

 THE BLOOD 



THE COAGULATION OF THE BLOOD. COUNTING OF THE BLOOD- 

 CORPUSCLES 



1. Preparation of the Animal. Place a cat under the bell-jar, con- 

 taining a small sponge moistened with ether, and carefully note its 

 behavior during the consecutive stages of the narcosis. When fully 

 under the influence of the ether transfer the animal to the operating 

 table, and apply a mask to its mouth, maintaining the anesthesia 

 throughout the following experiments. 



Annotation. Like in operations upon human beings, the depth of the narcosis is 

 ascertained by the intensity of the corneal re/lex. On touching the cornea the eyelids 

 are closed. The quickness with which this reaction takes place serves as a guide in 

 administering the ether. If the reflex becomes sluggish in its character, give less 

 ether. If the reflex is abolished entirely, institute artificial respiration immediately 

 until the respiratory movements are again executed spontaneously. Also watch 

 the character of the respiratory movements, and note the size of the pupil, because 

 the abolition of the reflexes is accompanied by an extreme dilatation of the pupil. 

 The action of the heart usually ceases some time after the stoppage of respiration, 

 and hence it is possible to resuscitate the animal if prompt measures are taken. 

 The abdominal reflex may also be employed as a guide. On tapping upon the abdo- 

 men of the animal with the flat of the hand the abdominal muscles contract, render- 

 ing the abdominal wall tense. Obviously, if the narcosis has been carried too far, 

 this reaction does not take place, and the hand does not rebound. 



A very efficient narcosis may also be established by means of urethane or chloral. 

 Chloretone is administered in doses of 0.25 gram per kilo of weight. Dogs should 

 receive to gr. of morphin and 2^0 to T ^o g r - of atropin sulphate about thirty minutes 

 before ether is given. When chloral is administered the animal should be kept 

 warm, otherwise an excessive loss of heat may result. Ether narcosis is adhered to 

 in these experiments in order to give the student as much experience as possible 

 preparatory to his clinical work. 



Tracheotomy : Insertion of Cannula. Insert a cannula in the trachea 

 and connect it with a glass bottle containing a sponge moistened with 

 ether. Expose the right common carotid artery and left external 

 jugular vein and insert a straight glass cannula in the central end of 

 the former and the distal end of the latter blood-vessel. 



Annotation. The operation of tracheotomy is performed in the following man- 

 ner: Make a median incision in the skin of the neck, beginning about 2 cm. below 

 the larynx. Lay the scalpel aside and cut through the underlying fascia with the 

 scissors. With the help of two forceps separate the muscles in the median line 

 until the trachea is brought into view. Separate the latter from the fascia surround- 

 ing it, and draw a loose cotton ligature around it. With your left hand raise the 

 trachea sufficiently to be able to make a transverse incision between two adjoining 

 rings of cartilage. Cut forward through two rings of cartilage. Quickly insert the 

 short arm of the tracheal cannula through this opening and tie the ligature around 



