1. One can think of mind (animus) and spirit (anima) as together constituting the soul, for which Lucretius does not have a separate word. The point is that these two account for all the functions traditionally assigned to the soul, in which different faculties/parts (vegetative, sensitive, rational) are located.

2. Lines 136-7 could be translated as “the mind [animum] and spirit [animam]… constitute one nature” or “one substance.” Lucretius is arguing that they are neither distinct things nor distinct kinds of things–a point reinforced at 3.421ff: “See that you couple both [mind and spirit] under a single name: when, for example, I proceed to speak of ’spirit’, proving that it is mortal, assume that I mean ‘mind’ as well, inasmuch as they constitute between them a unity and an interlocked entity. First since I have proved that it [spirit] is a delicate construction of minute bodies, and made of much smaller primary particles than the flowing liquid of water or cloud or smoke….” (L&S tr. but ours is essentially the same).

3. Given this, ‘cetera pars animae’ at line 143 could be translated “the rest of the soul,” as our translation has it, or “the remaining part of the spirit,” as in Long and Sedley. Either way we are talking about the fine matter that is distributed throughout the body (nerves) and is responsive to the command of the mind (heart/brain).

4. Long and Sedley take ‘animum mentemque’ at line 139 to be introducing these terms as synonyms. They use ‘mind’ for both, where our translation has (not unreasonably) “mind or intelligence.”

5. ‘Numen’ can mean divinity or god. But literally it means ‘a nod’, and more generally, some sort of authoritative assent: a command, will, authority (Lewis and Short). So we have: the rest of the spirit/soul obeys the mind and moves in response to (ad) its command and impulse.