I may be excused for a digression here because some readers may not be fully aware of what vapā is etc. Shri Zebra also had made some query regarding the yajurveda. I am attempting to cover both these aspects as best as is possible for me, in a post like this.
1. Shri zebra16 (Narayan) had stated in post# 94 as follows:—
http://www.tamilbrahmins.com/scriptures/5385-let-us-familiarise-ourselves-rigveda-10.html#post73812
"My question is primarily this:
I belong to yajurveda, taittiriya sakha. With basic limitation of my Sanskrit knowledge, I tried to know what is in the veda of my shakha, basically through translations. I could not know what is the central theme of my veda shakaha. How the mantras starting from “Ishe Tvaa, urje tvaa (in samhita) leads me to “Brahma sanDhattam tan me jinvatam” (in brahmanam) how it progresses to aruna praSnam (aaranyaka) and how it culminates in Sheekshaavalli etc. in the taittiriya upaniSad."
I will try to give the meanings of the portions from samhita and brāhmaṇa which you quote.
इषे त्वॊर्जॆ त्वा वायवः स्थोपायवः स्थ दॆवॊ वः सविता प्रार्पयतु श्रॆष्ठ्तमाय कर्मण आ प्यायध्वमघ्निया देवभागमूर्जस्वतीः पयस्वतीः प्रजावतीरनमीवा अयक्ष्मा मा वः स्तॆन ईशत माघशँ सो रुद्रस्य हेतिः परि वॊ वृणक्तु ध्रुवा अस्मिन् गोपतौ स्यात बह्वीर्यजमानस्य पशून्पाहि ॥तै. कृ. य. वॆ, १-१-०१॥
iṣe tvorje tvā vāyavaḥ sthopāyavaḥ stha devo vaḥ savitā prārpayatu śreṣṭhtamāya karmaṇa ā pyāyadhvamaghniyā devabhāgamūrjasvatīḥ payasvatīḥ prajāvatīranamīvā ayakṣmā mā vaḥ stena īśata māghaśam̐ so rudrasya hetiḥ pari vo vṛṇaktu dhruvā asmin gopatau syāta bahvīryajamānasya paśūnpāhi ||tai. kṛ. ya. ve, 1-1-01||
1. iṣe tvā ūrje tvā = For food thee, for strength thee ! (This mantra is chanted while cutting a twig or branch of a tree or plant, with which)
2. vāyavaḥ sthopāyavaḥ stha = Ye are winds, ye are approachers. (the calves, which drink from the cows' udders, are driven away.)
3. devo vaḥ savitā prārpayatu śreṣṭhtamāya karmaṇ(a)e = Let the god Savitr impel you to the most excellent offering.
4. ā pyāyadhvamaghniyā devabhāgamūrjasvatīḥ: payasvatīḥ prajāvatīranamīvā ayakṣmā = O invincible ones, swell with the share for the gods; full of strength, of milk, rich in offspring, free from sickness, from disease.
5. mā vaḥ stena īśata māghaśam̐ s(o)ah = Let no thief, no evil worker, have control over you.
6. rudrasya hetiḥ pari vo vṛṇaktu = Let Rudra's dart avoid you.
7. dhruvā asmin gopatau syāta bahvī(r)h = Abide ye, numerous, with this lord of cattle.
(3 to 7 are addressed to the cows, and they are milked, after reciting 8 to the tree branch which was used to drive away the calves in the beginning. This is the first step for the darśapūrṇamāsa sacrifice, to be done on every New Moon and Full Moon day.)
8. yajamānasya paśūnpāhi = Do thou protect the cattle of the sacrificer. (This mantra is to be addressed to the branch - stick - which was used to drive away the calves from the cows.
[Note: The English translation is from A.B. Keith's Taittiriya Sanhita]
Coming to taittirīya brāhmaṇa, of the kṛṣṇa yajurveda, it is more of a continuation of the taittirīya saṃhitā, as the brāhmaṇas are included in the saṃhitā. So, the taittirīya brāhmaṇa, contains only later additions to the saṃhitā. The most important additional material in the taittirīya brāhmaṇa is abaut "puruṣamedha" or human sacrifice, which is not present in the saṃhitā. Probably this idea of puruṣamedha was one of the later inventions of the priesthood as they went on finding ways and means to make the yajña or sacrifice itself more elaborate and complicated ritual which only the priesthood understood.
Let us now see what "brahma saṃdhattam tanme jinvatam etc.," mean. I have not found any source of translation and so the meaning in English is mine own; knowledgeable members may kindly point out corrections.
"brahma saṃdhattam tanme jinvatam |" is the first line; in subsequent lines the saṃdhattam and me jinvatam are repeated like refrain. Here brahma and kṣatra have to be considered together and understood as the unified force or power of brāhmaṇas (people, not the scriptural texts) and the reigning power of kṣatriyas (which perhaps was an outcome of a tussle for supremacy between the priestly class and the temporal ruling classes, and the reason for the original rājanya - royal - of the puruṣasūkta becoming kṣatriya or 'one who protects from injury'.)
The above line, therefore, means "the brāhmaṇa power" is united (with me), may it impel me.
Then follow a list of items— kṣatraḥ (the power of rulers), iṣaḥ (food), ūrjaḥ (force, energy), rayiḥ (wealth), puṣṭiḥ (nourishment), prajā (offspring), and paśavaḥ (animals). each of these is claimed to be united with the reciter and that such union may impel the reciter to action (doing the sacrifice). At the end, comes "stutosi janadhāḥ | devāstvā śukrapā praṇayantu |" (Worshipped, praised are (you) nourishing creatures : the pure soma-drinking devas lead you."
This could be considered as an invocatory yajus.
It will thus be seen that the "iṣe tvā ūrje tvā" of the samhitā does not have an invocatory tinge at all; the samhitā is very business like and straight away starts with the milking of cows for the sacrifice and has very little to do with the "brahma saṃdhattam tanme jinvatam |" of the brāhmaṇa. The former does not lead one to the latter in any conceivable rational manner.
Coming next to the āraṇyaka, the first mantra of the first anuvāka, we have the well-known "bhadram karṇebhiḥ śṛṇuyāma devāḥ etc." is an invocatory verse (mantra). The āruṇapraśna which consists of the first 32 anuvākas of the taittirīya āraṇyaka and contains many topica besides prayers to the sun god, discussion about kāla mṛtyu and akāla mṛtyu, prayers to devatās to thwart such mṛtyu, prayers to aśvinī devas, indra, vāyu, parjanya (rain god), and agni, various hells, jala devatā (ap) - the well-known mantra puṣpam -, creation, some matters relating to yāga, the seven dhātus of the body liberation, vaiśvānara yajña, samvatsara vrata, etc.
Hence, once again it is seen that you cannot have any logical sequencing of the saṃhitā, brāhmaṇa and āraṇyaka corpuses.
In many of the yajñas described in some saṃhitas and brāhmaṇas of the yajurveda and sāmaveda, including the somayāga, animals are required to be killed after being muzzled (closing their mouth being tied tightly so that they won't be able to produce any sound during death), such sounds being considered ill-omen for the yajña. The brāhmaṇa texts give details of how and where to cut the carcass of such killed animal, which portions to be given (for being consumed) to each priest taking part in the yajña, etc. The caul (greater omentum, gastrocolic omentum, Part of the peritoneum attached to the stomach and to the colon and covering the intestines) which looks like silk paper as per knowledgeable Brahmans, is collected after removing all the refuse present in a bull's hide (go tvac). This caul is vapā and it is obligatory to offer this into the yāgāgni, when the sacrificial fire burns very bright and with high flames.
In the ordinary somayāga the two rams which draw the vehicle in which the uprooted soma plants are to be brought to the place of sacrifice, are to be killed as described above and their vapā offered as oblation.
(I have heard from a dīkṣitar - one who has performed somayaga - who was my college mate's grandfather, talking to a group of very orthodox Brahmans - some 55 years ago - that the ram has to be killed in what appeared to me, a most heinous manner; he said "நவத்வாரங்களையும் அடைத்து ப்ராஹ்மணர்கள் கையால் இடித்துக் கொல்லவேண்டும்" [stuffing all the nine orifices, hitting it with fists by Brahmans].) The actual practice of minutiae of the different sacrifices or yāgas varied so widely with the result that the yajurveda reportedly had the maximum number of śākhās. In other places like north India, most probably the animals were muzzled alright but slaughtered with reciting of prescribed mantras by the priest whose duty it was, but others did not probably take any part till the animal was dead completely when the markings were made as to where the cuts ought to be, which portion should be given to which priest (for part oblation and part consumption as yajñaśiṣṭam). Even in the matter of eating the meat, different practices seemed to have prevailed; one was to eat it raw, another was to mix it with flour, cook or fry it and then eat.
In the more elaborate yajñas like aśvamedha a large number of animals - running into hundreds - are to be killed. (One can well imagine how many innocent animals would have been so killed mercilessly on the basis of some harebrained ideas of priesthood, in the daśāśvamedha ghāṭ in kāśi!). There are mentions about naramedha or puruṣamedha (human sacrifice) as also ass sacrifice in yv.
In 2007 there was reportedly a yāgam conducted in Kumbhakonam in which the Brahmans had readied 18 goats to be killed. Intervention by the police and animal rights actvists prevented slaying of all but one of these animals. One Sankaracharya was supposed to have been associated with that yaga.
"The Brahmasutra says: "Asuddhamiti cen na sabdat". The performance of sacrifices is based on scriptural authority and it is part of the quest for Self realisation. So how can it be called an impure act? How do we determine whether or not an object or an act is impure or whether it is good or bad? We do so by judging it according to the authority of of the sastras. Vyasa goes on to state in his Brahmasutra that animal sacrifice is not sinful since the act is permeated by the sound of the Vedas. What is pure or impure is to be known by the authority provided by the Vedas or rather their sound called Sabdapramana. If sacrifices were impure acts according to the Vedas, they would not have accepted them as part of the Atmic quest."
The above was part of the long justification for animal sacrifice attributed to senior Kanchi Acharya in one web page.(
Sankarachari Yagam Controversy in KumbakoNam - Sulekha coffeehouse Forums)
Yajurveda (taittirīya kṛṣṇa) saṃhitā deals with the undernoted yajñas which require animal sacrifice:-
The vājapeya (21 animals to be sacrificed; 17 cups of "surā" are also to be used in this), the rājasūya (a ritual extending to two years; it also involves animals to be sacrificed), the soma yajña, the sautrāmaṇī, the prāvargya, the agnicayana, the aśvamedha, and the puruṣamedha. In all these animal sacrifice is involved.
"Though the Rājasūya is full of interesting magic rites, and though it has a wide range of parallels in the consecration rites of all coronations, there is little that need be said in addition to Weber's elaborate account of its character. The important feature of the whole is the fact that the king is sharply distinguished from the priests : the proclamation tells the people that so-and-so is their king, but the Brahmans add that their king is Soma. The distinction shows that for vedic India at least the connexion of royalty with priestly rank, if it ever had been a motive of the growth of the kingship, had long disappeared before the time of the Sanhitas." [A.B. Keith]