614 INFECTIOUS DISEASES 



contractions of certain groups of muscles, or the entire mus- 

 culature of the animal's body, without that consciousness 

 is disturbed. 



Occurrence.— Tetanus is of rare occurrence in small animals. 

 It is observed occasionally in dogs and birds. It is far more 

 common in the large domesticated animals. 



Etiology.— It is produced by a specific bacillus (Bacillus 

 tetani of Nicolaier) . 



Natural Infection.— Infection takes place by the bacilli or 

 spores gaining entrance to wounds in the skin or mucous 

 membranes. The most common intermediate carrier of the 

 infection is the soil or earth which comes in contact with 

 the wounds. Rarely is the disease spread from one animal 

 to another. 



Pathology.— The postmortem is usually negative. The 

 affected muscles are usually pale, or may show occasional 

 hemorrhages. The condition of the blood indicates in most 

 cases that death is due to suffocation. Other lesions are 

 inconstant and of minor importance. 



Symptoms. — General tetanus is of rare occurrence, although 

 observed occasionally. It is characterized by a stiff, stilty 

 gait, extended head, ears stiffly erected, protrusion of the 

 membrana nictitans, skin wrinkled over the forehead, 

 trismus. The muscles of the back and posterior limbs are 

 stiff and hard; tail erected and stiff. The reflexes are greatly 

 accelerated as shown when the animal is touched or hears 

 sudden noises. There is frequently opisthotonus, or ortho- 

 tonus. Very characteristic is the facial expression of dogs 

 suffering from tetanus. Perhaps in the greater number of 

 cases in dogs and birds tetanus is local and involves only 

 certain groups of muscles, usually the masseters, the muscles 

 of the ears, skin and muscles over the forehead, membrana 

 nictitans, and the muscles of the neck, all of which are con- 

 tracted and the head held fixed. In birds the symptoms of 

 stiffness of the neck, wings held in a fixed position, ruffled 

 feathers, stilty gait are the most prominent. 



Diagnosis.— This is made mainly on the characteristic 

 symptom of tonic spasms of groups of muscles, with normal 

 consciousness and temperature, and the subacute course. 

 Differential Diagnosis.— (a) Differentiation must be made 



