PHYSICAL EXAMINATION OF THE HEAKT. 75 



(Valentin). In a human embryo (third month) the heart was found beating after 

 4 hours. In this condition stimulation causes an increase and acceleration of the 

 action. The ventricular contraction weakens, and soon each auricular contraction is 

 not followed by a ventricular contraction, two or more of the former being suc- 

 ceeded by only one of the latter. At the same time the ventricles contract more 

 slowly (fig. 46), and soon stop altogether, while the auricles continue to beat. If 

 the ventricles be stimulated directly, as by pricking them with a pin, they may 

 execute a contraction. The left auricle soon ceases to beat, while the right auricle 

 still continues to contract. The right auricular appendix continues to beat longest, 

 as was observed by Galen and Cardanus (1550), and it is termed "ultimum 

 moriens." Similar observations have been made upon the hearts of persons who 

 have been executed. 



If the heart has ceased to beat, it may be excited to contract for a short time by 

 direct stimulation, more especially by heat (Harvey) ; even under these circum- 

 stances the auricles and their appendices are the last parts to cease contracting. 

 As a general rule, direct stimulation, although it may cause the heart to act more 

 vigorously for a short time, brings it to rest sooner. In such cases, therefore, the 

 regular sequence of events ceases, and there is usually a twitching movement of the 

 muscular fibres of the heart. C. Ludwig found that, even after the excitability is 

 extinguished in the mammalian heart, it may be restored by injecting arterial blood 

 into the coronary arteries : conversely lesion of these vessels is followed by 

 enfeebled action of the heart ( 47). Hammer found that in a man, whose left 

 coronary artery was plugged, the pulse fell from 80 to 8 beats per minute. 



[The beats of the excised heart of a rabbit gradually decline in force and frequency, the latent 

 period and contraction become longer and the excitability more obtuse. The duration of a con- 

 traction may be 6 sec, the normal being "3 sec. The beats have often a bigeminal character. An 

 excised heart may be frozen quite hard, yet on being thawed it contracts spontaneously. The 

 contraction proceeds in a wave from the spot stimulated in the frog's heart at 8 to 12 C. at 30 

 to 90 mm. per sec. ; in the mammalian excised heart about 8 metres per sec. ( Waller and Reid).~\ 



Action of Gases on the Heart. During its activity the heart uses O, and produces C0 2 , so 

 that it beats longest in pure O (12 hours), and not so long in N, H (1 hour) C0 2 (10 minutes) 

 CO (42 minutes) CI (2 minutes), or in a vacuum (20 to 30 minutes), even when there is watery 

 vapour present to prevent evaporation. If the heart be reintroduced into O it begins to beat 

 again. [A frog's heart ceases to beat in compressed O (10 to 12 atmospheres) in about one-third 

 of the time it would do were it simply excised and left to itself. An excised heart suspended 

 in ordinary air beats three to four times as long as a heart which is placed upon a glass-plate.] 



[56. PHYSICAL EXAMINATION OF THE HEART. The physical 

 methods of diagnosis enable us to obtain precise knowledge regarding the actual 

 state of the heart. The methods available are : 



1. Inspection. 



2. Palpation. 



3. Percussion. 



4. Auscultation. 



To arrive at a correct'diagnosis all the methods must be employed.] 



[Inspection. The person is supposed to have his chest exposed and to be in the recumbent 

 position. It is important to remember the limits of the heart. The base corresponds to a line 

 .joining the upper margins of the third costal cartilages, the apex to the fifth interspace, while trans- 

 versely it extends from a little to the right of the sternum to within a little of the left nipple ; 

 this area occupied by the heart being called the deep cardiac region. By the eye we can detect 

 any alteration in the configuration of the pnecordia, bulging or retraction of the region as a 

 whole or of the intercostal spaces, and we may detect ..variations in the position, character, 

 extent of the cardiac impulse, or the presence of other visible pulsations.] 



[Palpation. By placing the whole hand flat upon the prsecordia, we can ascertain the 

 presence or absence, the situation and extent, and any alterations in the characters of the apex- 

 teat; or we may detect the existence of abnormal pulsations, vibrations, thrills, or friction in 

 this region. In feeling for the apex-beat, if it be at all feeble, it is well to make the patient 

 lean forward. Of course, it must be remembered that the whole heart may be displaced by 

 tumours or accumulations of fluids pressing upon it, i.e., conditions external to itself, or the 

 apex-beat may be displaced from causes within the heart itself, as in hypertrophy of the left 

 ventricle.} % <. - -'-'*- ; - >"< -i ' - 



