THE DISTRIBUTION OF ARTERIES. 127 



the frequency is not all that is necessary to a beneficial 

 end ; we should render the pulse soft also, without which a 

 slow pulse may retain its fatal character. 



A soft pulse opposes little resistance to the fingers ; but 

 seems to allow a due volume of blood to flow through it 

 without labour or interruption. This pulse is frequent at the 

 decline of inflammatory affections ; and usually shows the 

 cessation of the disease. Suppuration, as a termination of 

 inflammation, produces it ; and when pus forms, a soft 

 pulse is generally the consequence. 



A regular pulse is occasionally found when disease is pre- 

 sent ; but it is usually under such circumstances of an altered 

 character. A regular pulse, with a proportionate fulness, is 

 one of the strongest marks of health ; as an irregular one 

 usually betokens acute disease : irregularity in it may, how- 

 ever, exist without acute symptoms ; and may depend on 

 organic affections or peculiarities in the system. Irregularity 

 in the pulse, in most cases, is a mark of irritability ; and it 

 may characterize debility. In inflammation of the heart 

 there is usually a peculiar irregularity in the pulse, with 

 extreme oppression and smallness. An irregular pulse in 

 fever shows great danger ; it also accompanies the fatal ter- 

 minations of all inflammations. The worst cases of pleu- 

 ritis and pneumonia commonly present it before the close ; 

 and in certain cases a very singular irregularity is present, 

 from a large quantity of serous fluid formed within the 

 chest ; in which, besides its intermission, the pulse appears 

 as though undulating through a bladder of water. This 

 pulse should be particularly noticed ; as, when once it be- 

 comes familiar, along with other signs, it affords an unerring 

 guide to the state of the patient. 



THE DISTRIBUTION OF ARTERIES. 



The aorta {Fig 13 . 1), the principal vessel of the arterial 

 system, rises perpendicularly from the top of the left ven- 

 tricle of the heart : having proceeded about two inches, it 

 divides into two branches, opposite the fifth dorsal vertebra ; 

 one of which is carried forwards to furnish the head and 

 fore extremities ; the other proceeds backwards, to be dis- 

 tributed to the body and the hinder limbs. These divisions 

 form the anterior {Fig 9.1) and posterior aorta (Fig 13 . 4) ; 



