In order to arrive at a correct diagnosis, the skilled examiner has a certain method which enables him to obtain the information which he desires without any waste of time. Symptoms which to the amateur resolve themselves into a general expression of the presence of some illness, are to the eye of the expert in many cases distinctly indicative of the locality and nature of the disorder.
When diagnostic symptoms are absent it becomes necessary to make a systematic examination, which, although comprehensive, is carried on with so little effort and occupies so short a time as to attract very little notice from the lookers-on. For instance, beginning with the animal's head, a few seconds will suffice to enable the experienced examiner to ascertain the condition of the visible mucous membranes; a mere glance at the mouth, the interior of the nostrils, and the eye will be sufficient to show whether or not the membrane is red or yellow, or pallid or spotted, or in any way changed from its normal condition. The general attitude of the animal will have been noticed at the first moment of inspection, and the condition of the surface ascertained by passing the hand over different parts of the body and the extremities, the examiner noting whether or not the skin is in a healthy state or is harsh to the touch, adherent to the tissues beneath, hot, warm, or cold. The condition which is described as a staring coat, where the hair is more or less elevated or erect, is seen at once, and is always accepted as a symptom of bad condition, and may commonly be taken as premonitory of some serious disorder.
After a general examination of the kind described has been completed, attention is paid to the condition of certain organs, including those of the circulatory, respiratory, and digestive systems. The state of the circulatory organs is to a large extent shown by the character of the pulse, i.e. the periodic expansion of the arteries, during the contraction of the heart in its effort to drive the blood throughout the body. This expansion, or beat as it is called, may be felt by placing the finger over any of the superficial arteries. The sub-maxillary artery (a, fig. 492) in the horse, as it passes under the edge of the lower jaw close to the bone, is a convenient vessel for the purpose. In the popular idea the object of feeling the pulse is to discover the number of pulsations in a minute. The pathologist, however, attaches far more importance to the character of the pulsation than to the number of beats in a given time, and it may be added that the character of the pulse varies under different circumstances to an extent which it may be difficult for the unprofessional mind to realize. Many of these variations can be recognized by the touch; their complete appreciation, however, requires the use of an instrument which is known as the sphygmo-graph, which enables the observer to obtain tracings showing precisely the condition of the circulation. The varieties of pulse which can be recognized by the touch are described by Sir J. S. Burdon Sanderson in his hand-book of the sphygmograph under four heads: 1st, There is a frequent and infrequent pulse, terms which mean the number of pulsations within a given time. 2nd, The quick or slow pulse, expressions which are erroneously used to define the same thing, i.e. the number of beats per minute. To the pathologist the words quick and slow bear a totally different signification, meaning not the number of beats in a minute, but the time occupied by each beat of the pulse irrespective of number in a certain time; thus a quick pulse may be slow so far as the number of beats in the minute is concerned. 3rd, The large or small pulse, terms relating to the degree of dilatation of the artery in length and breadth. 4th, A hard or soft pulse, so called from the impression which the beat communicates to the touch: a soft pulse is easily compressed, while a hard pulse only gives way to considerable force.
Fig. 492. - Points for Feeling the Pulse.
a, The sub-maxillary artery, b, The zygomatic artery. c, The carotid artery (behind the jugular vein). The pulse is felt at the points indicated by crosses, at a by pressing against the inner side of the lower jaw with the fingers, at 6 and c by pressing down upon the artery.
All the above described conditions of the pulse, which can be appreciated without the aid of any instruments, convey to the mind of the expert certain ideas as to the state of the animal's system or of some particular part or organ. The frequent pulse, for instance - that is, a pulse which beats more frequently than the standard number of 40 in the minute, - in the horse indicates some degree of excitation in the circulatory system, which may depend on a variety of causes - exercise, a sudden alarm, the mere entrance of a stranger or a strange animal, may increase the frequency of the pulse within certain limits; but when in the horse the beats reach to 50 or 60 in the minute, or above, fever is obviously indicated.
Fig. 493. - Feeling the Pulse.
A very frequent pulse may, however, be associated with extreme debility; but in addition to the rapidity of the pulse in such circumstances there will be an important change in its character.
An infrequent pulse is found in diseases of the heart or brain, and in such cases the pulse is often intermittent, a condition which is extremely characteristic and easily recognized; a number of regular beats being followed by a period of rest, and then succeeded by another sequence of regular beats.
Quick pulse as distinguished from frequent pulse is more easily discovered by the sphygmograph than by the finger. It depends upon the sudden contraction of the ventricle; the expansion of the artery consequently occupies less time than in the healthy pulse, although by calculating the number of beats during a given period the quick pulse may be found to be also less frequent than the normal. The quick pulse would usually be taken to indicate excess in irritability of the muscular structure of the heart.